diff --git a/Doc/Sd1/languageFundamentals.xml b/Doc/Sd1/languageFundamentals.xml
index 00c3b118b2efea48e009a6cdc62b58d475247748..086d55408467d1d449119b5320b3653fb765d94b 100644
--- a/Doc/Sd1/languageFundamentals.xml
+++ b/Doc/Sd1/languageFundamentals.xml
@@ -1,25 +1,14 @@
<?xml version="1.0" encoding="UTF-8"?>
-<chapter annotations="slide" version="5.1" xml:id="sw1LanguageFundamental"
- xmlns="http://docbook.org/ns/docbook"
- xmlns:xlink="http://www.w3.org/1999/xlink"
- xmlns:xila="http://www.w3.org/2001/XInclude/local-attributes"
- xmlns:xi="http://www.w3.org/2001/XInclude"
- xmlns:trans="http://docbook.org/ns/transclusion"
- xmlns:svg="http://www.w3.org/2000/svg"
- xmlns:m="http://www.w3.org/1998/Math/MathML"
- xmlns:html="http://www.w3.org/1999/xhtml"
- xmlns:db="http://docbook.org/ns/docbook">
+<chapter annotations="slide" version="5.1" xml:id="sw1LanguageFundamental" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xila="http://www.w3.org/2001/XInclude/local-attributes" xmlns:xi="http://www.w3.org/2001/XInclude" xmlns:trans="http://docbook.org/ns/transclusion" xmlns:svg="http://www.w3.org/2000/svg" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:html="http://www.w3.org/1999/xhtml" xmlns:db="http://docbook.org/ns/docbook">
<title>Language Fundamentals</title>
<section xml:id="sd1_sect_langFundamental_intro">
<title>Introduction</title>
<section xml:id="sd1_fig_asciiAndUnicode">
- <title>Integer, <xref linkend="glo_ASCII"/> and <xref
- linkend="glo_unicode"/></title>
+ <title>Integer, <xref linkend="glo_ASCII"/> and <xref linkend="glo_unicode"/></title>
- <para>We will deal with computation machines.
- Having just mechanical devices at hand this still works:</para>
+ <para>We will deal with computation machines. Having just mechanical devices at hand this still works:</para>
<figure xml:id="sd1_fig_cashier">
<title>Cash register</title>
@@ -51,9 +40,7 @@
</mediaobject>
</figure>
- <para>So far all machines being described are based on non-semiconductor
- technologies. Inventing the transistor in the fifties gave rise to a
- rapid development of microprocessor chips:</para>
+ <para>So far all machines being described are based on non-semiconductor technologies. Inventing the transistor in the fifties gave rise to a rapid development of microprocessor chips:</para>
<figure xml:id="sd1_fig_microprocessors">
<title>Microprocessor ICs</title>
@@ -65,9 +52,7 @@
</mediaobject>
</figure>
- <para>These sample devices differ heavily with respect to addressable
- memory, data size, supported arithmetic operations / speed and other
- features. We take a closer look to Zilog's Z80 processor:</para>
+ <para>These sample devices differ heavily with respect to addressable memory, data size, supported arithmetic operations / speed and other features. We take a closer look to Zilog's Z80 processor:</para>
<figure xml:id="sd1_fig_z80">
<title>Zilog Z80 CPU</title>
@@ -79,8 +64,7 @@
</mediaobject>
</figure>
- <para>Following technological advances processors have been categorized
- by the length the so called address- and data-bus:</para>
+ <para>Following technological advances processors have been categorized by the length the so called address- and data-bus:</para>
<figure xml:id="sd1_fig_adressDataBus">
<title>Address and data bus sizes</title>
@@ -148,9 +132,7 @@
</informaltable>
</figure>
- <para>We remind the reader to the binary representation of signed
- integer values. Details will be discussed in your math lectures. Our
- first example features three bit 2-complement:</para>
+ <para>We remind the reader to the binary representation of signed integer values. Details will be discussed in your math lectures. Our first example features three bit 2-complement:</para>
<figure xml:id="sd1_fig_signed3bitIntDual">
<title>Signed 3 bit integer representation</title>
@@ -162,8 +144,7 @@
</mediaobject>
</figure>
- <para>Signed <code>byte</code> values are being represented
- accordingly:</para>
+ <para>Signed <code>byte</code> values are being represented accordingly:</para>
<figure xml:id="sd1_fig_signedIntRepresentBinary">
<title>Signed 8 bit integer binary representation</title>
@@ -175,8 +156,7 @@
</mediaobject>
</figure>
- <para>Regarding language characters we start with one of the oldest and
- widespread character encoding schemes:</para>
+ <para>Regarding language characters we start with one of the oldest and widespread character encoding schemes:</para>
<figure xml:id="sd1_fig_7bitASCII">
<title>7-bit <xref linkend="glo_ASCII"/></title>
@@ -188,10 +168,7 @@
</mediaobject>
</figure>
- <para><xref linkend="glo_ASCII"/> by design is limited to US characters
- and does not include characters from non-English languages. Since <xref
- linkend="glo_ASCII"/> only uses seven bits we may a parity bit to form
- one byte per character:</para>
+ <para><xref linkend="glo_ASCII"/> by design is limited to US characters and does not include characters from non-English languages. Since <xref linkend="glo_ASCII"/> only uses seven bits we may a parity bit to form one byte per character:</para>
<figure xml:id="sd1_fig_7bitASCII_andParity">
<title>7-bit <xref linkend="glo_ASCII"/> with even parity bit</title>
@@ -203,16 +180,10 @@
</mediaobject>
</figure>
- <para>A byte's parity bit may instead be used for encoding non- <xref
- linkend="glo_ASCII"/> supplementary characters. One such example is the
- <link xlink:href="https://en.wikipedia.org/wiki/ISO/IEC_8859-1">ISO
- 8859-1 (ISO Latin 1)</link> standard representing western European
- character sets:</para>
+ <para>A byte's parity bit may instead be used for encoding non- <xref linkend="glo_ASCII"/> supplementary characters. One such example is the <link xlink:href="https://en.wikipedia.org/wiki/ISO/IEC_8859-1">ISO 8859-1 (ISO Latin 1)</link> standard representing western European character sets:</para>
<figure xml:id="sd1_fig_iso8859_1">
- <title><link
- xlink:href="https://en.wikipedia.org/wiki/ISO/IEC_8859-1">ISO Latin
- 1</link> encoding</title>
+ <title><link xlink:href="https://en.wikipedia.org/wiki/ISO/IEC_8859-1">ISO Latin 1</link> encoding</title>
<mediaobject>
<imageobject>
@@ -221,13 +192,10 @@
</mediaobject>
</figure>
- <para>Supporting additional languages comes at a price: We have to
- increase the number of bytes representing a single character:</para>
+ <para>Supporting additional languages comes at a price: We have to increase the number of bytes representing a single character:</para>
<figure xml:id="sd1_fig_unicodeSample">
- <title>Some <xref linkend="glo_unicode"/> <link
- xlink:href="https://en.wikipedia.org/wiki/UTF-8">UTF-8</link>
- samples</title>
+ <title>Some <xref linkend="glo_unicode"/> <link xlink:href="https://en.wikipedia.org/wiki/UTF-8">UTF-8</link> samples</title>
<mediaobject>
<imageobject>
@@ -236,19 +204,13 @@
</mediaobject>
</figure>
- <para>Notice the representation's differing byte count: <link
- xlink:href="https://en.wikipedia.org/wiki/UTF-8">UTF-8</link> <xref
- linkend="glo_unicode"/> encoding allows for one-, two-, three- and four-
- byte encodings. See <quote
- xlink:href="https://betterexplained.com/articles/unicode">Unicode and
- You</quote> for further details.</para>
+ <para>Notice the representation's differing byte count: <link xlink:href="https://en.wikipedia.org/wiki/UTF-8">UTF-8</link> <xref linkend="glo_unicode"/> encoding allows for one-, two-, three- and four- byte encodings. See <quote xlink:href="https://betterexplained.com/articles/unicode">Unicode and You</quote> for further details.</para>
</section>
<section xml:id="sd1_sect_variables">
<title>Variables</title>
- <para>Variables are convenient handles for accessing memory. We don't
- need to mess with memory addresses:</para>
+ <para>Variables are convenient handles for accessing memory. We don't need to mess with memory addresses:</para>
<figure xml:id="sd1_fig_varMemoryHandle">
<title>Handle to memory</title>
@@ -260,8 +222,7 @@
</mediaobject>
</figure>
- <para>Declaring a variable requires a type name like <code>double</code>
- and an identifier:</para>
+ <para>Declaring a variable requires a type name like <code>double</code> and an identifier:</para>
<figure xml:id="sd1_fig_varDeclare">
<title>Variable declaration</title>
@@ -269,8 +230,7 @@
<programlisting language="java">double pi;</programlisting>
</figure>
- <para>We may assign values to variables or build expressions like
- <code>pi * 2.0 * 2.0</code> :</para>
+ <para>We may assign values to variables or build expressions like <code>pi * 2.0 * 2.0</code> :</para>
<figure xml:id="sd1_fig_varDeclareAndUse">
<title>Declare and use</title>
@@ -338,13 +298,11 @@ int c;</programlisting>
<itemizedlist>
<listitem>
- <para>Start with a small letter like <code>africa</code> rather
- than <code>Africa</code>.</para>
+ <para>Start with a small letter like <code>africa</code> rather than <code>Africa</code>.</para>
</listitem>
<listitem>
- <para>Use <quote>camel case</quote> e.g.
- <code>myFirstCode</code>.</para>
+ <para>Use <quote>camel case</quote> e.g. <code>myFirstCode</code>.</para>
<mediaobject>
<imageobject>
@@ -457,6 +415,272 @@ int Count = 44;
System.out.println(count + ":" + Count); // This yields "32:44"</programlisting>
</figure>
+ <qandaset defaultlabel="qanda" xml:id="sw1QandaLegalVarNames">
+ <title>Legal variable names</title>
+
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>Which of the following names are legal variable names? Complete the following table and explain your decision with respect to the <quote xlink:href="https://proquest.safaribooksonline.com/9780992133047/toc4_html_3">variables</quote> section.</para>
+
+ <informaltable border="1">
+ <colgroup width="19%"/>
+
+ <colgroup width="10%"/>
+
+ <colgroup width="71%"/>
+
+ <tr>
+ <th>Identifier</th>
+
+ <th>is legal? (yes / no)</th>
+
+ <th>Explanation / remark</th>
+ </tr>
+
+ <tr>
+ <td><code>for</code></td>
+
+ <td/>
+
+ <td/>
+ </tr>
+
+ <tr>
+ <td><code>sum_of_data</code></td>
+
+ <td/>
+
+ <td/>
+ </tr>
+
+ <tr>
+ <td><code>sumOfData</code></td>
+
+ <td/>
+
+ <td/>
+ </tr>
+
+ <tr>
+ <td><code>first-name</code></td>
+
+ <td/>
+
+ <td/>
+ </tr>
+
+ <tr>
+ <td><code>ABC</code></td>
+
+ <td/>
+
+ <td/>
+ </tr>
+
+ <tr>
+ <td><code>42isThesolution</code></td>
+
+ <td/>
+
+ <td/>
+ </tr>
+
+ <tr>
+ <td><code>println</code></td>
+
+ <td/>
+
+ <td/>
+ </tr>
+
+ <tr>
+ <td><code>B4</code></td>
+
+ <td/>
+
+ <td/>
+ </tr>
+
+ <tr>
+ <td><code>AnnualSalary</code></td>
+
+ <td/>
+
+ <td/>
+ </tr>
+
+ <tr>
+ <td><code>"hello"</code></td>
+
+ <td/>
+
+ <td/>
+ </tr>
+
+ <tr>
+ <td><code>_average </code></td>
+
+ <td/>
+
+ <td/>
+ </tr>
+
+ <tr>
+ <td><code>ανδÏος</code></td>
+
+ <td/>
+
+ <td/>
+ </tr>
+
+ <tr>
+ <td><code>$sum </code></td>
+
+ <td/>
+
+ <td/>
+ </tr>
+ </informaltable>
+
+ <tip>
+ <para>You may want to prepare a simple <xref linkend="glo_Java"/> program testing the above names.</para>
+ </tip>
+ </question>
+
+ <answer>
+ <para>We may write a small <xref linkend="glo_Java"/> program:</para>
+
+ <programlisting language="java">public static void main(String[] args) {
+ int 42isThesolution = 6; // <emphasis role="bold">Syntax error on token "42", delete this token</emphasis>
+}</programlisting>
+
+ <para>Unfortunately the error explanation is not too helpful with respect to <xref linkend="glo_Java"/> beginners. It does not immediately point towards an illegal identifier problem. One indication of a sound compiler is its ability to provide meaningful, self explanatory error messages.</para>
+
+ <informaltable border="1">
+ <colgroup width="19%"/>
+
+ <colgroup width="10%"/>
+
+ <colgroup width="71%"/>
+
+ <tr>
+ <th>Identifier</th>
+
+ <th>is legal? (yes / no)</th>
+
+ <th>Explanation / remark</th>
+ </tr>
+
+ <tr>
+ <td><code>for</code></td>
+
+ <td>no</td>
+
+ <td><quote>for</quote> is a Java keyword.</td>
+ </tr>
+
+ <tr>
+ <td><code>sum_of_data</code></td>
+
+ <td>yes</td>
+
+ <td>-</td>
+ </tr>
+
+ <tr>
+ <td><code>sumOfData</code></td>
+
+ <td>yes</td>
+
+ <td>-</td>
+ </tr>
+
+ <tr>
+ <td><code>first-name</code></td>
+
+ <td>no</td>
+
+ <td>Operators like <quote>-</quote> or <quote>+</quote> must not appear in variable names.</td>
+ </tr>
+
+ <tr>
+ <td><code>ABC</code></td>
+
+ <td>yes</td>
+
+ <td>Best practices: Discouraged variable name, non-constant variables should start with lowercase letters.</td>
+ </tr>
+
+ <tr>
+ <td><code>42isThesolution</code></td>
+
+ <td>no</td>
+
+ <td>Identifiers must not start with a number.</td>
+ </tr>
+
+ <tr>
+ <td><code>println</code></td>
+
+ <td>yes</td>
+
+ <td><code>println</code> is a method of <code>System.out.println(...)</code> but is no <xref linkend="glo_Java"/> keyword.</td>
+ </tr>
+
+ <tr>
+ <td><code>B4</code></td>
+
+ <td>yes</td>
+
+ <td>Best practices: Discouraged variable name, non-constant variables should start with lowercase letters.</td>
+ </tr>
+
+ <tr>
+ <td><code>AnnualSalary</code></td>
+
+ <td>yes</td>
+
+ <td>Best practices: Legal but discouraged variable name: Non-constant variables should start with lowercase letters.</td>
+ </tr>
+
+ <tr>
+ <td><code>"hello"</code></td>
+
+ <td>no</td>
+
+ <td>String delimiters must not be part of an identifier.</td>
+ </tr>
+
+ <tr>
+ <td><code>_average </code></td>
+
+ <td>yes</td>
+
+ <td>Best practices: Should be reserved for system code.</td>
+ </tr>
+
+ <tr>
+ <td><code>ανδÏος</code></td>
+
+ <td>yes</td>
+
+ <td>Perfectly legal Greek <orgname>Unicode</orgname> characters.</td>
+ </tr>
+
+ <tr>
+ <td><code>$sum </code></td>
+
+ <td>yes</td>
+
+ <td>Best practices: Using the <quote>$</quote> sign should be reserved for system code.</td>
+ </tr>
+ </informaltable>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
+
<figure xml:id="sd1_fig_varDeclareBeforeUse">
<title>Declare before use</title>
@@ -493,8 +717,7 @@ i = b; // Error: int and boolean are incompatible types
i = "Hello"; // Even worse: Assigning a String to an int</programlisting>
</figure>
- <para><xref linkend="glo_Java"/> provides meta information on
- types:</para>
+ <para><xref linkend="glo_Java"/> provides meta information on types:</para>
<figure xml:id="sd1_fig_intTypeMaxMin">
<title>Maximum and minimum values</title>
@@ -513,11 +736,9 @@ i = "Hello"; // Even worse: Assigning a String to an int</programlisting>
<tr>
<td>byte</td>
- <td><link
- xlink:href="https://docs.oracle.com/javase/8/docs/api/java/lang/Byte.html#BYTES">1</link></td>
+ <td><link xlink:href="https://docs.oracle.com/javase/8/docs/api/java/lang/Byte.html#BYTES">1</link></td>
- <td><link
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Byte.MIN_VALUE"><inlineequation>
+ <td><link xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Byte.MIN_VALUE"><inlineequation>
<m:math display="inline">
<m:mrow>
<m:mo>-</m:mo>
@@ -531,8 +752,7 @@ i = "Hello"; // Even worse: Assigning a String to an int</programlisting>
</m:math>
</inlineequation></link></td>
- <td><link
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Byte.MAX_VALUE"><inlineequation>
+ <td><link xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Byte.MAX_VALUE"><inlineequation>
<m:math display="inline">
<m:mrow>
<m:msup>
@@ -552,13 +772,11 @@ i = "Hello"; // Even worse: Assigning a String to an int</programlisting>
<tr>
<td>char</td>
- <td><link
- xlink:href="https://docs.oracle.com/javase/8/docs/api/java/lang/Byte.html#BYTES">2</link></td>
+ <td><link xlink:href="https://docs.oracle.com/javase/8/docs/api/java/lang/Byte.html#BYTES">2</link></td>
<td>0</td>
- <td><link
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Character.MAX_VALUE"><inlineequation>
+ <td><link xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Character.MAX_VALUE"><inlineequation>
<m:math display="inline">
<m:mrow>
<m:msup>
@@ -578,11 +796,9 @@ i = "Hello"; // Even worse: Assigning a String to an int</programlisting>
<tr>
<td>short</td>
- <td><link
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Short.BYTES">2</link></td>
+ <td><link xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Short.BYTES">2</link></td>
- <td><link
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Short.MIN_VALUE"><inlineequation>
+ <td><link xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Short.MIN_VALUE"><inlineequation>
<m:math display="inline">
<m:mrow>
<m:mo>-</m:mo>
@@ -596,8 +812,7 @@ i = "Hello"; // Even worse: Assigning a String to an int</programlisting>
</m:math>
</inlineequation></link></td>
- <td><link
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Short.MAX_VALUE"><inlineequation>
+ <td><link xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Short.MAX_VALUE"><inlineequation>
<m:math display="inline">
<m:mrow>
<m:msup>
@@ -617,11 +832,9 @@ i = "Hello"; // Even worse: Assigning a String to an int</programlisting>
<tr>
<td>int</td>
- <td><link
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Integer.BYTES">4</link></td>
+ <td><link xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Integer.BYTES">4</link></td>
- <td><link
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Integer.MIN_VALUE"><inlineequation>
+ <td><link xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Integer.MIN_VALUE"><inlineequation>
<m:math display="inline">
<m:mrow>
<m:mo>-</m:mo>
@@ -635,8 +848,7 @@ i = "Hello"; // Even worse: Assigning a String to an int</programlisting>
</m:math>
</inlineequation></link></td>
- <td><link
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Integer.MAX_VALUE"><inlineequation>
+ <td><link xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Integer.MAX_VALUE"><inlineequation>
<m:math display="inline">
<m:mrow>
<m:msup>
@@ -656,11 +868,9 @@ i = "Hello"; // Even worse: Assigning a String to an int</programlisting>
<tr>
<td>long</td>
- <td><link
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Long.BYTES">8</link></td>
+ <td><link xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Long.BYTES">8</link></td>
- <td><link
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Long.MIN_VALUE"><inlineequation>
+ <td><link xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Long.MIN_VALUE"><inlineequation>
<m:math display="inline">
<m:mrow>
<m:mo>-</m:mo>
@@ -674,8 +884,7 @@ i = "Hello"; // Even worse: Assigning a String to an int</programlisting>
</m:math>
</inlineequation></link></td>
- <td><link
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Long.MAX_VALUE"><inlineequation>
+ <td><link xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Long.MAX_VALUE"><inlineequation>
<m:math display="inline">
<m:mrow>
<m:msup>
@@ -704,8 +913,7 @@ i = "Hello"; // Even worse: Assigning a String to an int</programlisting>
<glossdef>
<programlisting language="java">int a = -15;</programlisting>
- <para>Possible types: All eight primitive <xref
- linkend="glo_Java"/> types.</para>
+ <para>Possible types: All eight primitive <xref linkend="glo_Java"/> types.</para>
</glossdef>
</glossentry>
@@ -715,8 +923,7 @@ i = "Hello"; // Even worse: Assigning a String to an int</programlisting>
<glossdef>
<programlisting language="java">GpsPosition start = new GpsPosition(48.7758, 9.1829);</programlisting>
- <para>Possible types: Arbitrary built in or user defined
- classes.</para>
+ <para>Possible types: Arbitrary built in or user defined classes.</para>
</glossdef>
</glossentry>
</glosslist>
@@ -755,8 +962,7 @@ LocalDate birtday = LocalDate.of(1990, Month.JULY, 5);</programlisting>
</tr>
<tr>
- <td><programlisting language="java">System.out.println("Decimal "+ <emphasis
- role="bold">35</emphasis>);
+ <td><programlisting language="java">System.out.println("Decimal "+ <emphasis role="bold">35</emphasis>);
System.out.println("Binary " + <emphasis role="bold">0b10_0011</emphasis>);
System.out.println("Hex " + <emphasis role="bold">0x23</emphasis>);
System.out.println("Octal " + <emphasis role="bold">043</emphasis>); </programlisting></td>
@@ -772,661 +978,370 @@ Octal 35</screen></td>
<figure xml:id="sd1_fig_intLiteralLimitExcess">
<title>Know your limits!</title>
- <programlisting language="java">System.out.println(10000000000<emphasis
- role="bold">L</emphasis>); // o.K.
+ <programlisting language="java">System.out.println(10000000000<emphasis role="bold">L</emphasis>); // o.K.
System.out.println(10000000000 ); // Compile time error: Integer number too large</programlisting>
</figure>
- <figure xml:id="sd1_fig_javaLiterals">
- <title><xref linkend="glo_Java"/> literals</title>
-
- <informaltable border="1">
- <tr>
- <td><code>byte</code>, <code>short</code></td>
-
- <td>-</td>
- </tr>
-
- <tr>
- <td><code>char</code></td>
-
- <td><code>'A'</code>, <code>'\u0041'</code></td>
- </tr>
-
- <tr>
- <td><code>int</code></td>
-
- <td><code>29</code>, <code>0b1_1101</code>, <code>0x1D</code>,
- <code>035</code>, <code>-29</code>,</td>
- </tr>
-
- <tr>
- <td><code>long</code></td>
-
- <td><code>35L</code>, <code>0b10_0011L</code>, <code>0x23L</code>,
- <code>043L</code>, <code>-35L</code>,...</td>
- </tr>
-
- <tr>
- <td><code>float</code></td>
-
- <td><code>55.43F</code>, <code>1.7E-23F</code>, <code>-17.F,
- 100_342.334_113</code></td>
- </tr>
-
- <tr>
- <td><code>double</code></td>
-
- <td><code>55.43</code>, <code>1.7 E -23</code>,
- <code>-17.</code></td>
- </tr>
-
- <tr>
- <td><code>String</code></td>
-
- <td><code>"Hello"</code>, <code>"Greek Δ"</code>, <code>"Greek
- <link
- xlink:href="https://www.fileformat.info/info/unicode/char/0394/index.htm">\u0394</link>"</code></td>
- </tr>
-
- <tr>
- <td><code>boolean</code></td>
-
- <td><code>true</code>, <code>false</code></td>
- </tr>
-
- <tr>
- <td/>
-
- <td><code>null</code></td>
- </tr>
- </informaltable>
- </figure>
-
- <figure xml:id="sd1_fig_romanNumerals">
- <title>Just kidding ...</title>
-
- <programlisting language="java">int year = MMXIV; // <link
- xlink:href="https://en.wikipedia.org/wiki/Roman_numerals">Roman numerals</link> representation
-
-System.out.println("Olympic winter games: " + year);</programlisting>
-
- <screen>Olympic winter games: 2014</screen>
- </figure>
- </section>
-
- <section xml:id="sd1_sect_arithmeticLimitations">
- <title>Arithmetic limitations</title>
-
- <para>Expect the unexpected:</para>
-
- <figure xml:id="sd1_fig_byteLitteralAssign">
- <title>Strange things</title>
-
- <programlisting language="java">byte count = 91; // o.K.
-
-byte points = 130; // Compile error: Incompatible types
- // Required: byte Found: int</programlisting>
- </figure>
-
- <figure xml:id="sd1_fig_byteOverflow">
- <title>Overflow</title>
-
- <programlisting language="java">int count = 2147483647;
-int points = 2147483647;
-
-int sum = count + points;
-System.out.println("Sum = " + sum);</programlisting>
-
- <para>Result:</para>
-
- <informaltable border="1">
- <tr>
- <td valign="top"><screen>Sum = -2</screen></td>
-
- <td><screen> 01111111_11111111_11111111_11111111
-+ 01111111_11111111_11111111_11111111
-_____________________________________
- 11111111_11111111_11111111_11111110</screen></td>
- </tr>
- </informaltable>
- </figure>
-
- <para>Why not using float / double in favour of bounded
- <code>byte</code>, <code>short</code>, <code>int</code>,
- <code>long</code> for arithmetics?</para>
-
- <figure xml:id="sd1_fig_floatPrecision">
- <title>Limited precision</title>
-
- <programlisting language="java">float float2Power31 = Integer.MAX_VALUE + 1f;
-
-float floatDoubleMAX_VALUE = 2 * float2Power31* float2Power31 - 1f; // 2^63 - 1
-
-System.out.format( " Float value: %f\n", floatDoubleMAX_VALUE);
-System.out.println("Expected value: " + Long.MAX_VALUE);</programlisting>
-
- <para>Result:</para>
-
- <screen> Float value: 9223372036854776000.000000
-Expected value: 9223372036854775807</screen>
- </figure>
-
- <figure xml:id="sd1_fig_floatConverter">
- <title><uri
- xlink:href="https://www.h-schmidt.net/FloatConverter">https://www.h-schmidt.net/FloatConverter</uri></title>
-
- <mediaobject>
- <imageobject>
- <imagedata fileref="Ref/LangFundament/floatConverter.png"/>
- </imageobject>
- </mediaobject>
- </figure>
- </section>
- </section>
-
- <section xml:id="sd1_sect_langFundamental_exercises">
- <title>Exercises</title>
-
- <section xml:id="sw1LegalVariableName">
- <title>Legal variable names</title>
-
- <qandaset defaultlabel="qanda" xml:id="sw1QandaLegalVarNames">
- <title>Legal variable names</title>
+ <qandaset defaultlabel="qanda" xml:id="sw1QandaMaxMinInt">
+ <title>An <code>int</code>'s minimum and maximum value</title>
<qandadiv>
<qandaentry>
<question>
- <para>Which of the following names are legal variable names?
- Complete the following table and explain your decision with
- respect to the <quote
- xlink:href="https://proquest.safaribooksonline.com/9780992133047/toc4_html_3">variables</quote>
- section.</para>
+ <para>In this exercise we look at an <code>int</code>'s the largest and smallest possible value.</para>
- <informaltable border="1">
- <colgroup width="19%"/>
-
- <colgroup width="10%"/>
-
- <colgroup width="71%"/>
-
- <tr>
- <th>Identifier</th>
-
- <th>is legal? (yes / no)</th>
-
- <th>Explanation / remark</th>
- </tr>
+ <para>A <xref linkend="glo_Java"/> <code xlink:href="https://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html">int</code> is internally being represented by 4 <link linkend="glo_byte">bytes</link>. <inlineequation>
+ <m:math display="inline">
+ <m:msub>
+ <m:mi>00000000000000000000000000000101</m:mi>
- <tr>
- <td><code>for</code></td>
-
- <td/>
-
- <td/>
- </tr>
-
- <tr>
- <td><code>sum_of_data</code></td>
-
- <td/>
-
- <td/>
- </tr>
-
- <tr>
- <td><code>sumOfData</code></td>
-
- <td/>
-
- <td/>
- </tr>
-
- <tr>
- <td><code>first-name</code></td>
+ <m:mi>2</m:mi>
+ </m:msub>
+ </m:math>
+ </inlineequation> for example represents the decimal value 5.</para>
- <td/>
+ <para>In order to represent negative values as well <xref linkend="glo_Java"/> uses <link xlink:href="https://en.wikipedia.org/wiki/Two's_complement#firstHeading">Two's complement</link> representation. We provide some values:</para>
- <td/>
- </tr>
+ <table border="1" xml:id="sw1Table4ByteIntegerRepresentation">
+ <caption>4 Byte <link xlink:href="https://en.wikipedia.org/wiki/Two's_complement#firstHeading">Two's complement</link> representation of <code>int</code> values.</caption>
<tr>
- <td><code>ABC</code></td>
+ <th>Two complement representation</th>
- <td/>
-
- <td/>
+ <th>Decimal representation</th>
</tr>
<tr>
- <td><code>42isThesolution</code></td>
-
- <td/>
+ <td><code>00000000000000000000000000000000</code></td>
- <td/>
+ <td>0</td>
</tr>
<tr>
- <td><code>println</code></td>
-
- <td/>
-
- <td/>
- </tr>
+ <td><code>01111111111111111111111111111111</code></td>
- <tr>
- <td><code>B4</code></td>
+ <td><inlineequation>
+ <m:math display="inline">
+ <m:mrow>
+ <m:msup>
+ <m:mi>2</m:mi>
- <td/>
+ <m:mrow>
+ <m:mi>16</m:mi>
- <td/>
- </tr>
+ <m:mo>-</m:mo>
- <tr>
- <td><code>AnnualSalary</code></td>
+ <m:mi>1</m:mi>
+ </m:mrow>
+ </m:msup>
- <td/>
+ <m:mo>-</m:mo>
- <td/>
+ <m:mi>1</m:mi>
+ </m:mrow>
+ </m:math>
+ </inlineequation> (Maximum)</td>
</tr>
<tr>
- <td><code>"hello"</code></td>
+ <td><code>10000000000000000000000000000000</code></td>
- <td/>
+ <td><inlineequation>
+ <m:math display="inline">
+ <m:mrow>
+ <m:mo>-</m:mo>
- <td/>
- </tr>
+ <m:msup>
+ <m:mi>2</m:mi>
- <tr>
- <td><code>_average </code></td>
+ <m:mrow>
+ <m:mi>16</m:mi>
- <td/>
+ <m:mo>-</m:mo>
- <td/>
+ <m:mi>1</m:mi>
+ </m:mrow>
+ </m:msup>
+ </m:mrow>
+ </m:math>
+ </inlineequation> (Minimum)</td>
</tr>
<tr>
- <td><code>ανδÏος</code></td>
-
- <td/>
+ <td><code>11111111111111111111111111111111</code></td>
- <td/>
+ <td>-1</td>
</tr>
+ </table>
- <tr>
- <td><code>$sum </code></td>
+ <para>Use <link xlink:href="https://docs.oracle.com/javase/specs/jls/se8/html/jls-3.html#jls-3.10.1"><code>int</code> literals</link> in <link xlink:href="https://docs.oracle.com/javase/specs/jls/se8/html/jls-3.html#jls-BinaryNumeral">binary representation</link> like e.g. <code>0B1100</code> in section <quote xlink:href="https://proquest.safaribooksonline.com/9780992133047/toc6_html_2">Literals</quote> in order to write an <code>int</code>'s minimum and maximum possible value to standard output.</para>
- <td/>
-
- <td/>
- </tr>
- </informaltable>
+ <programlisting language="java"> public static void main(String[] args) {
+
+ int minumum = ... , //TODO: provide values by
+ maximum = ...; // binary int literals
- <tip>
- <para>You may want to prepare a simple <xref
- linkend="glo_Java"/> program testing the above names.</para>
- </tip>
+ System.out.println("Minimum:" + minumum);
+ System.out.println("Maximum:" + maximum);
+ }</programlisting>
</question>
<answer>
- <para>We may write a small <xref linkend="glo_Java"/>
- program:</para>
+ <para>We insert <link xlink:href="https://en.wikipedia.org/wiki/Two's_complement#firstHeading">Two's complement</link> representations of minimum and maximum int values according to <xref linkend="sw1Table4ByteIntegerRepresentation"/>.</para>
<programlisting language="java">public static void main(String[] args) {
- int 42isThesolution = 6; // <emphasis role="bold">Syntax error on token "42", delete this token</emphasis>
-}</programlisting>
-
- <para>Unfortunately the error explanation is not too helpful
- with respect to <xref linkend="glo_Java"/> beginners. It does
- not immediately point towards an illegal identifier problem. One
- indication of a sound compiler is its ability to provide
- meaningful, self explanatory error messages.</para>
-
- <informaltable border="1">
- <colgroup width="19%"/>
-
- <colgroup width="10%"/>
+
+ int minumum = 0B10000000_00000000_00000000_00000000,
+ maximum = 0B01111111_11111111_11111111_11111111;
- <colgroup width="71%"/>
+ System.out.println("Minimum int value:" + minumum);
+ System.out.println("Maximum int value:" + maximum);
+ }</programlisting>
- <tr>
- <th>Identifier</th>
+ <para>BTW: The <xref linkend="glo_JDK"/> does provide maximum value, minimum value and related information for <code>char</code>, <code>byte</code>, <code>short</code> and <code>int</code> data types int its related <classname xlink:href="https://docs.oracle.com/javase/8/docs/api/java/lang/Character.html">Character</classname>, <classname xlink:href="https://docs.oracle.com/javase/8/docs/api/java/lang/Byte.html">Byte</classname>, <classname xlink:href="https://docs.oracle.com/javase/8/docs/api/java/lang/Short.html">Short</classname> and <classname xlink:href="https://docs.oracle.com/javase/8/docs/api/java/lang/Integer.html">Integer</classname> classes. You may want to execute:</para>
- <th>is legal? (yes / no)</th>
+ <programlisting language="java"> System.out.println("int minimum:" + Integer.MIN_VALUE);
+ System.out.println("int minimum:" + Integer.MAX_VALUE);
+
+ System.out.println("int bytes:" + Integer.BYTES);
+ System.out.println("int size:" + Integer.SIZE);
+</programlisting>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
- <th>Explanation / remark</th>
- </tr>
+ <qandaset defaultlabel="qanda" xml:id="sw1QandaIntLimitShort">
+ <title>Testing the limits (Difficult)</title>
- <tr>
- <td><code>for</code></td>
-
- <td>no</td>
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>A careful programmer is worried whether a short variable is <emphasis role="bold">always</emphasis> large enough to hold color intensity values ranging from 0 to 255. Give an answer being based on the <link xlink:href="https://docs.oracle.com/javase/specs/jls/se8/html/jls-4.html#jls-4.2.1">specification</link> and not just by <acronym>try-and-error</acronym>.</para>
- <td><quote>for</quote> is a Java keyword.</td>
- </tr>
+ <para>The programmer tries to adopt the <link linkend="sw1QandaMaxMinInt">related int example</link> accordingly:</para>
- <tr>
- <td><code>sum_of_data</code></td>
+ <programlisting language="java">short minumum = 0B10000000_00000000,
+ maximum = 0B01111111_11111111;
- <td>yes</td>
+System.out.println("Minimum short value:" + minumum);
+System.out.println("Maximum short value:" + maximum</programlisting>
- <td>-</td>
- </tr>
+ <para>Our programmer is baffled:</para>
- <tr>
- <td><code>sumOfData</code></td>
+ <itemizedlist>
+ <listitem>
+ <para>The first assignment <code language="java">minumum = 0B10000000_00000000</code> is being flagged as a compile time error:</para>
- <td>yes</td>
+ <para><computeroutput>Type mismatch: cannot convert from int to short</computeroutput></para>
+ </listitem>
- <td>-</td>
- </tr>
+ <listitem>
+ <para>On contrary the second assignment <code language="java">maximum = 0B01111111_11111111</code> gets smoothly accepted.</para>
+ </listitem>
+ </itemizedlist>
- <tr>
- <td><code>first-name</code></td>
+ <tip>
+ <para>Which integer literal types do exist according to the <xref linkend="glo_Java"/> <link xlink:href="https://docs.oracle.com/javase/specs/jls/se8/html/jls-3.html#jls-3.10.1">standard</link>?</para>
+ </tip>
+ </question>
- <td>no</td>
+ <answer>
+ <para>Since variables of type <code>short</code> have a two bytes representation their corresponding range is <inlineequation>
+ <m:math display="inline">
+ <m:mrow>
+ <m:mo>[</m:mo>
- <td>Operators like <quote>-</quote> or <quote>+</quote> must
- not appear in variable names.</td>
- </tr>
+ <m:mrow>
+ <m:mrow>
+ <m:mo>-</m:mo>
- <tr>
- <td><code>ABC</code></td>
+ <m:msup>
+ <m:mi>2</m:mi>
- <td>yes</td>
+ <m:mi>15</m:mi>
+ </m:msup>
+ </m:mrow>
- <td>Best practices: Discouraged variable name, non-constant
- variables should start with lowercase letters.</td>
- </tr>
+ <m:mo>,</m:mo>
- <tr>
- <td><code>42isThesolution</code></td>
+ <m:mrow>
+ <m:msup>
+ <m:mi>2</m:mi>
- <td>no</td>
+ <m:mi>15</m:mi>
+ </m:msup>
- <td>Identifiers must not start with a number.</td>
- </tr>
+ <m:mo>-</m:mo>
- <tr>
- <td><code>println</code></td>
+ <m:mi>1</m:mi>
+ </m:mrow>
+ </m:mrow>
- <td>yes</td>
+ <m:mo>]</m:mo>
+ </m:mrow>
+ </m:math>
+ </inlineequation>. Thus intensity values ranging from 0 to 255 will be easily accommodated.</para>
- <td><code>println</code> is a method of
- <code>System.out.println(...)</code> but is no <xref
- linkend="glo_Java"/> keyword.</td>
- </tr>
+ <para>The second question is more difficult to explain: The <xref linkend="glo_Java"/> standard only defines <code>int</code> literals. It does however not define <code>short</code> (or <code>byte</code>) literals.</para>
- <tr>
- <td><code>B4</code></td>
+ <para>Thus the 0B01111111_11111111 literal will be treated as an <code>int</code> value being compatible with a <code>short</code> variable and is thus assignable.</para>
- <td>yes</td>
+ <para>On the contrary the binary value <code>10000000_00000000</code> evaluates to <inlineequation>
+ <m:math display="inline">
+ <m:msup>
+ <m:mn>2</m:mn>
- <td>Best practices: Discouraged variable name, non-constant
- variables should start with lowercase letters.</td>
- </tr>
+ <m:mi>15</m:mi>
+ </m:msup>
+ </m:math>
+ </inlineequation> (equal to 32768) exceeding a two-byte (signed) short variable's upper limit.</para>
- <tr>
- <td><code>AnnualSalary</code></td>
+ <para>Even worse: A <code>short</code> variable containing binary <code>10000000_00000000</code> due to its two byte <link xlink:href="https://en.wikipedia.org/wiki/Two's_complement#firstHeading">Two's complement</link> representation has got a value <inlineequation>
+ <m:math display="inline">
+ <m:mrow>
+ <m:mo>-</m:mo>
- <td>yes</td>
+ <m:msup>
+ <m:mn>2</m:mn>
- <td>Best practices: Legal but discouraged variable name:
- Non-constant variables should start with lowercase
- letters.</td>
- </tr>
+ <m:mi>15</m:mi>
+ </m:msup>
+ </m:mrow>
+ </m:math>
+ </inlineequation> (or -32768).</para>
- <tr>
- <td><code>"hello"</code></td>
+ <para>In order to avoid this error we need an explicit type conversion (a so called cast):</para>
- <td>no</td>
+ <programlisting language="java">short minumum = (short) 0B10000000_00000000;</programlisting>
- <td>String delimiters must not be part of an
- identifier.</td>
- </tr>
+ <para>Since a <code>short</code> variable's range is <inlineequation>
+ <m:math display="inline">
+ <m:mrow>
+ <m:mo>[</m:mo>
- <tr>
- <td><code>_average </code></td>
+ <m:mrow>
+ <m:mrow>
+ <m:mo>-</m:mo>
- <td>yes</td>
+ <m:msup>
+ <m:mi>2</m:mi>
- <td>Best practices: Should be reserved for system code.</td>
- </tr>
+ <m:mi>15</m:mi>
+ </m:msup>
+ </m:mrow>
- <tr>
- <td><code>ανδÏος</code></td>
+ <m:mo>,</m:mo>
- <td>yes</td>
+ <m:mrow>
+ <m:msup>
+ <m:mi>2</m:mi>
- <td>Perfectly legal Greek <orgname>Unicode</orgname>
- characters.</td>
- </tr>
+ <m:mi>15</m:mi>
+ </m:msup>
- <tr>
- <td><code>$sum </code></td>
+ <m:mo>-</m:mo>
- <td>yes</td>
+ <m:mi>1</m:mi>
+ </m:mrow>
+ </m:mrow>
- <td>Best practices: Using the <quote>$</quote> sign should
- be reserved for system code.</td>
- </tr>
- </informaltable>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
- </section>
+ <m:mo>]</m:mo>
+ </m:mrow>
+ </m:math>
+ </inlineequation> we may as well use a unary minus sign instead:</para>
- <section xml:id="sw1IntegerLiterals">
- <title>Integer value literals</title>
+ <programlisting language="java">short minumum = -0B10000000_00000000;</programlisting>
- <section xml:id="sd1SectBinaryIntLiteral">
- <title>Binary literals</title>
+ <para>Both variants are syntactically correct and will thus compile. However they are likely not being intended by our programmer.</para>
- <qandaset defaultlabel="qanda" xml:id="sd1QandaBinaryIntLiteral">
- <qandadiv>
- <qandaentry>
- <question>
- <orderedlist>
- <listitem>
- <para>Using the decimal system to represent integer values
- we tend to ignore other important numbering systems. Write
- an application which prints the decimal value of
- <inlineequation>
- <m:math display="inline">
- <m:msub>
- <m:mi>1110100100</m:mi>
+ <para>The error in the first place is probably assigning a value of <inlineequation>
+ <m:math display="inline">
+ <m:mrow>
+ <m:mo>+</m:mo>
- <m:mi>2</m:mi>
- </m:msub>
- </m:math>
- </inlineequation> by writing the former as a binary int
- literal. Verify the printed value by an independent
- calculation.</para>
- </listitem>
+ <m:msup>
+ <m:mi>2</m:mi>
- <listitem>
- <para>Construct a second binary literal representing a
- negative value of your choice.</para>
+ <m:mi>15</m:mi>
+ </m:msup>
+ </m:mrow>
+ </m:math>
+ </inlineequation> to a <code>short</code> variable at all.</para>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
- <tip>
- <para>An <code>int</code> is being represented by four
- bytes in <xref linkend="glo_Java"/>.</para>
- </tip>
- </listitem>
- </orderedlist>
- </question>
+ <figure xml:id="sd1_fig_javaLiterals">
+ <title><xref linkend="glo_Java"/> literals</title>
- <answer>
- <orderedlist>
- <listitem>
- <programlisting language="java">public static void main(String[] args) {
+ <informaltable border="1">
+ <tr>
+ <td><code>byte</code>, <code>short</code></td>
- System.out.println(" Binary:" + 0B11_10100100);
- System.out.println("Decimal:" + (512
- + 256
- + 128
- + 32
- + 4));
- }</programlisting>
+ <td>-</td>
+ </tr>
- <para>This yields:</para>
+ <tr>
+ <td><code>char</code></td>
- <screen> Binary:932
-Decimal:932</screen>
- </listitem>
+ <td><code>'A'</code>, <code>'\u0041'</code></td>
+ </tr>
- <listitem>
- <para>A negative value in <link
- xlink:href="https://en.wikipedia.org/wiki/Two's_complement#firstHeading">Two's
- complement</link> representation starts with a
- <quote>1</quote> at its highest bit. Binary literals in
- <xref linkend="glo_Java"/> represent <code>int</code>
- values. An <code>int</code> in <xref linkend="glo_Java"/>
- uses 4 bytes and thus occupies 4 x 8=32 bits. Therefore
- choosing a negative value is a simple task: Start with
- <quote>1</quote> and let it follow by 32 - 1 = 31 random
- bit values:</para>
+ <tr>
+ <td><code>int</code></td>
- <programlisting language="java">public static void main(String[] args) {
- System.out.println(0B10000000_00111001_01101001_01110100);
-}</programlisting>
- </listitem>
- </orderedlist>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
- </section>
+ <td><code>29</code>, <code>0b1_1101</code>, <code>0x1D</code>, <code>035</code>, <code>-29</code>,</td>
+ </tr>
- <section xml:id="sd1SectBracesInPrintln">
- <title>Why using braces inside <code>System.out.println(...)</code>
- ?</title>
+ <tr>
+ <td><code>long</code></td>
- <qandaset defaultlabel="qanda" xml:id="sd1QandaBracesInPrintln">
- <qandadiv>
- <qandaentry>
- <question>
- <para>Solution <xref linkend="sd1SectBinaryIntLiteral"/>
- contains:</para>
+ <td><code>35L</code>, <code>0b10_0011L</code>, <code>0x23L</code>, <code>043L</code>, <code>-35L</code>,...</td>
+ </tr>
- <programlisting language="java">...
- System.out.println("Decimal:" + (512 +
- 256 +
- 128 +
- 32 +
- 4)); ...</programlisting>
+ <tr>
+ <td><code>float</code></td>
- <para>Why are the <quote>inner</quote> braces immediately
- preceding 512 and following 4 are being required?</para>
+ <td><code>55.43F</code>, <code>1.7E-23F</code>, <code>-17.F, 100_342.334_113</code></td>
+ </tr>
- <tip>
- <itemizedlist>
- <listitem>
- <para>Execute the above code omitting the
- <quote>inner</quote> braces.</para>
- </listitem>
+ <tr>
+ <td><code>double</code></td>
- <listitem>
- <para>Read about the <quote>+</quote> operator's role
- e.g. in <code>System.out.println("Some" + "
- string").</code></para>
- </listitem>
- </itemizedlist>
- </tip>
- </question>
+ <td><code>55.43</code>, <code>1.7 E -23</code>, <code>-17.</code></td>
+ </tr>
- <answer>
- <para>We start omitting the <quote>inner</quote>
- braces:</para>
+ <tr>
+ <td><code>String</code></td>
- <programlisting language="java">...
- System.out.println("Decimal:" + 512 +
- 256 +
- 128 +
- 32 +
- 4); ...</programlisting>
+ <td><code>"Hello"</code>, <code>"Greek Δ"</code>, <code>"Greek <link xlink:href="https://www.fileformat.info/info/unicode/char/0394/index.htm">\u0394</link>"</code></td>
+ </tr>
- <para>This results in the following output:</para>
+ <tr>
+ <td><code>boolean</code></td>
- <screen>...
-Decimal:512256128324</screen>
+ <td><code>true</code>, <code>false</code></td>
+ </tr>
- <para>The numbers are being treated as strings rather than
- integer values The above code is equivalent to:</para>
-
- <programlisting language="java">...
- System.out.println("Decimal:" + "512" +
- "256" +
- "128" +
- "32" +
- "4"); ...</programlisting>
-
- <para>The <quote>+</quote> operator between two strings
- defines their concatenation. So all six components get joined
- into a single result string.</para>
-
- <para>Supplying additional inner braces defines an expression
- (512 + 256 + 128 + 32 + 4) solely involving integer values. In
- this context each <quote>+</quote> operator effects the usual
- integer arithmetic:</para>
-
- <programlisting language="java">...
- System.out.println("Decimal:" +<co linkends="sd1ListingPlusOpDuplicate-1"
- xml:id="sd1ListingPlusOpDuplicate-1-co"/> (512 +<co
- linkends="sd1ListingPlusOpDuplicate-2"
- xml:id="sd1ListingPlusOpDuplicate-2-co"/>
- 256 +<co
- linkends="sd1ListingPlusOpDuplicate-2"
- xml:id="sd1ListingPlusOpDuplicate-3-co"/>
- 128 +<co
- linkends="sd1ListingPlusOpDuplicate-2"
- xml:id="sd1ListingPlusOpDuplicate-4-co"/>
- 32 +<co
- linkends="sd1ListingPlusOpDuplicate-2"
- xml:id="sd1ListingPlusOpDuplicate-5-co"/>
- 4)); ...</programlisting>
-
- <calloutlist>
- <callout arearefs="sd1ListingPlusOpDuplicate-1-co"
- xml:id="sd1ListingPlusOpDuplicate-1">
- <para><quote>+</quote> operator concatenating the two
- strings <code>"Decimal:"</code> and
- <code>"932"</code>.</para>
- </callout>
-
- <callout arearefs="sd1ListingPlusOpDuplicate-2-co sd1ListingPlusOpDuplicate-3-co sd1ListingPlusOpDuplicate-4-co sd1ListingPlusOpDuplicate-5-co"
- xml:id="sd1ListingPlusOpDuplicate-2">
- <para><quote>+</quote> operators computing the integer sum
- of 512, 256, 128, 32 and 4 yielding a value of 932. This
- value subsequently gets transformed into the String
- <code>"932"</code> in order to be compatible with the
- preceding <code>"Decimal:"</code> string.</para>
- </callout>
- </calloutlist>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
- </section>
+ <tr>
+ <td/>
+
+ <td><code>null</code></td>
+ </tr>
+ </informaltable>
+ </figure>
- <section xml:id="sd1_sect_poorMansAscii">
+ <qandaset defaultlabel="qanda" xml:id="sd1_qanda_poorMansAscii">
<title>Poor mans ASCII table</title>
- <qandaset defaultlabel="qanda" xml:id="sd1_qanda_poorMansAscii">
- <qandadiv>
- <qandaentry>
- <question>
- <para>We want to construct a list of <link
- xlink:href="http://www.rapidtables.com/code/text/ascii-table.htm#print">printable
- ASCII characters</link>. Write a <xref linkend="glo_Java"/>
- application by starting just from from character literals
- <code>' '</code>, <code>'!'</code>, <code>'"'</code>,
- <code>'#'</code> and so on to show their corresponding decimal
- values. The intended output is:</para>
-
- <screen> : 32
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>We want to construct a list of <link xlink:href="http://www.rapidtables.com/code/text/ascii-table.htm#print">printable ASCII characters</link>. Write a <xref linkend="glo_Java"/> application by starting just from from character literals <code>' '</code>, <code>'!'</code>, <code>'"'</code>, <code>'#'</code> and so on to show their corresponding decimal values. The intended output is:</para>
+
+ <screen> : 32
!: 33
": 34
#: 35
@@ -1434,21 +1349,17 @@ $: 36
%: 37
&: 38</screen>
- <para>Notice the empty space being represented by decimal
- 32.</para>
+ <para>Notice the empty space being represented by decimal 32.</para>
- <tip>
- <para>A <code>char</code> value being represented by two
- bytes may be easily assigned to an <code>int</code>
- variable.</para>
- </tip>
- </question>
+ <tip>
+ <para>A <code>char</code> value being represented by two bytes may be easily assigned to an <code>int</code> variable.</para>
+ </tip>
+ </question>
- <answer>
- <para>Since <code>char</code> values may be assigned to
- <code>int</code> variables we may code:</para>
+ <answer>
+ <para>Since <code>char</code> values may be assigned to <code>int</code> variables we may code:</para>
- <programlisting language="java">{
+ <programlisting language="java">{
char c = ' '; // space
int value = c;
System.out.println(c + ": " + value);
@@ -1465,10 +1376,9 @@ $: 36
}
...</programlisting>
- <para>Using an explicit type conversion from char to int (a so
- called cast) yields an identical result:</para>
+ <para>Using an explicit type conversion from char to int (a so called cast) yields an identical result:</para>
- <programlisting language="java">System.out.println(' ' + ": " + ((int) ' '));
+ <programlisting language="java">System.out.println(' ' + ": " + ((int) ' '));
System.out.println('!' + ": " + ((int) '!'));
System.out.println('"' + ": " + ((int) '"'));
System.out.println('#' + ": " + ((int) '#'));
@@ -1476,36 +1386,24 @@ System.out.println('$' + ": " + ((int) '$'));
System.out.println('%' + ": " + ((int) '%'));
System.out.println('&' + ": " + ((int) '&'));
...</programlisting>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
- </section>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
+
+ <qandaset defaultlabel="qanda" xml:id="sw1QandaIntByBinary">
+ <title>Integer value hexadecimal representation</title>
+
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>As you may know the <xref linkend="glo_RGB"/> color model uses triplets of numbers to define color value components representing intensities of its three base colors <foreignphrase><emphasis role="bold">R</emphasis>ed</foreignphrase>, <foreignphrase><emphasis role="bold">G</emphasis>reen</foreignphrase> and <foreignphrase><emphasis role="bold">B</emphasis>lue</foreignphrase>. The component values range from 0 to 255, the latter defining maximum intensity.</para>
- <section xml:id="sw1SectHexadecimalLiterals">
- <title>Hexadecimal literals</title>
-
- <para>As you may know the <xref linkend="glo_RGB"/> color model uses
- triplets of numbers to define color value components representing
- intensities of its three base colors <foreignphrase><emphasis
- role="bold">R</emphasis>ed</foreignphrase>, <foreignphrase><emphasis
- role="bold">G</emphasis>reen</foreignphrase> and
- <foreignphrase><emphasis role="bold">B</emphasis>lue</foreignphrase>.
- The component values range from 0 to 255, the latter defining maximum
- intensity.</para>
-
- <para>The color <quote>red</quote> for example is being represented by
- (255, 0, 0). So the red component has maximum intensity while blue and
- green are zero.</para>
-
- <para>It is however common to use <link
- xlink:href="http://www.december.com/html/spec/color16codes.html">hexadecimal
- in favour of decimal values</link>. Thus the same color
- <quote>red</quote> in the subsequent HTML example's heading font is
- now being represented by <emphasis
- role="bold">(FF,0,0)</emphasis>:</para>
-
- <programlisting language="html"><!DOCTYPE html>
+ <para>The color <quote>red</quote> for example is being represented by (255, 0, 0). So the red component has maximum intensity while blue and green are zero.</para>
+
+ <para>It is however common to use <link xlink:href="http://www.december.com/html/spec/color16codes.html">hexadecimal in favour of decimal values</link>. Thus the same color <quote>red</quote> in the subsequent HTML example's heading font is now being represented by <emphasis role="bold">(FF,0,0)</emphasis>:</para>
+
+ <programlisting language="html"><!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>A simple color example</title>
@@ -1514,585 +1412,476 @@ System.out.println('&' + ": " + ((int) '&'));
<body><h1 style="<emphasis role="bold">color: #FF0000;</emphasis>">My heading</h1></body>
</html></programlisting>
- <qandaset defaultlabel="qanda" xml:id="sw1QandaIntByBinary">
- <title>Integer values by binary representations</title>
-
- <qandadiv>
- <qandaentry>
- <question>
- <para>Write a program printing the hexadecimal representation
- <inlineequation>
- <m:math display="inline">
- <m:msub>
- <m:mi>C0</m:mi>
-
- <m:mi>16</m:mi>
- </m:msub>
- </m:math>
- </inlineequation> as a decimal value.</para>
-
- <para>Complete the following code by assigning the hexadecimal
- value <inlineequation>
- <m:math display="inline">
- <m:msub>
- <m:mi>C0</m:mi>
-
- <m:mi>16</m:mi>
- </m:msub>
- </m:math>
- </inlineequation> (The <quote>silver</quote> color's all
- three component's intensity in <uri
- xlink:href="http://www.december.com/html/spec/color16codes.html">http://www.december.com/html/spec/color16codes.html</uri>)
- to get the output in decimal representation.</para>
-
- <programlisting language="java">public static void main(String[] args) {
+ <para>Write a program printing the hexadecimal representation <inlineequation>
+ <m:math display="inline">
+ <m:msub>
+ <m:mi>C0</m:mi>
+
+ <m:mi>16</m:mi>
+ </m:msub>
+ </m:math>
+ </inlineequation> as a decimal value.</para>
+
+ <para>Complete the following code by assigning the hexadecimal value <inlineequation>
+ <m:math display="inline">
+ <m:msub>
+ <m:mi>C0</m:mi>
+
+ <m:mi>16</m:mi>
+ </m:msub>
+ </m:math>
+ </inlineequation> (The <quote>silver</quote> color's all three component's intensity in <uri xlink:href="http://www.december.com/html/spec/color16codes.html">http://www.december.com/html/spec/color16codes.html</uri>) to get the output in decimal representation.</para>
+
+ <programlisting language="java">public static void main(String[] args) {
short intensity = ...;
System.out.println(intensity);
}</programlisting>
- <tip>
- <para>You may want to consider the <quote
- xlink:href="https://proquest.safaribooksonline.com/9780992133047/toc6_html_2">Literals</quote>
- section of <xref linkend="bib_Kurniawan2015"/> learning
- about hexadecimal integer value representation.</para>
- </tip>
- </question>
+ <tip>
+ <para>You may want to consider the <quote xlink:href="https://proquest.safaribooksonline.com/9780992133047/toc6_html_2">Literals</quote> section of <xref linkend="bib_Kurniawan2015"/> learning about hexadecimal integer value representation.</para>
+ </tip>
+ </question>
- <answer>
- <para>The solution is straightforward:</para>
+ <answer>
+ <para>Using hexadecimal literals we have:</para>
- <programlisting language="java"> public static void main(String[] args) {
+ <programlisting language="java">short intensity = 0xC0;
- short intensity = 0xC0;
-
- System.out.println(intensity);
+System.out.println(intensity);</programlisting>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
+
+ <qandaset defaultlabel="qanda" xml:id="sd1_qanda_literalProblem">
+ <title>Literal problem</title>
+
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>Consider:</para>
+
+ <programlisting language="java">System.out.println(048);</programlisting>
+
+ <para>This yields a compile time error <quote>Integer number too large</quote>. On contrary the following code will compile and run perfectly well:</para>
+
+ <programlisting language="java">System.out.println(047);</programlisting>
+
+ <para>Explain the underlying problem.</para>
+ </question>
+
+ <answer>
+ <para>The literal <quote>048</quote> is meant to be octal representation. Unfortunately the only digits in octal representations range from 0 to 7. So <quote>047</quote> is fine but <quote>048</quote> simply is no valid literal in <xref linkend="glo_Java"/>.</para>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
+
+ <figure xml:id="sd1_fig_romanNumerals">
+ <title>Just kidding ...</title>
+
+ <programlisting language="java">int year = MMXIV; // <link xlink:href="https://en.wikipedia.org/wiki/Roman_numerals">Roman numerals</link> representation
+
+System.out.println("Olympic winter games: " + year);</programlisting>
+
+ <screen>Olympic winter games: 2014</screen>
+ </figure>
+
+ <qandaset defaultlabel="qanda" xml:id="sd1QandaBinaryIntLiteral">
+ <title>Binary literals</title>
+
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <orderedlist>
+ <listitem>
+ <para>Using the decimal system to represent integer values we tend to ignore other important numbering systems. Write an application which prints the decimal value of <inlineequation>
+ <m:math display="inline">
+ <m:msub>
+ <m:mi>1110100100</m:mi>
+
+ <m:mi>2</m:mi>
+ </m:msub>
+ </m:math>
+ </inlineequation> by writing the former as a binary int literal. Verify the printed value by an independent calculation.</para>
+ </listitem>
+
+ <listitem>
+ <para>Construct a second binary literal representing a negative value of your choice.</para>
+
+ <tip>
+ <para>An <code>int</code> is being represented by four bytes in <xref linkend="glo_Java"/>.</para>
+ </tip>
+ </listitem>
+ </orderedlist>
+ </question>
+
+ <answer>
+ <orderedlist>
+ <listitem>
+ <programlisting language="java">public static void main(String[] args) {
+
+ System.out.println(" Binary:" + 0B11_10100100);
+ System.out.println("Decimal:" + (512
+ + 256
+ + 128
+ + 32
+ + 4));
}</programlisting>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
-
- <qandaset defaultlabel="qanda" xml:id="sw1QandaIntLimitShort">
- <title>Testing the limits, part 2 (Difficult)</title>
-
- <qandadiv>
- <qandaentry>
- <question>
- <para>A careful programmer is worried whether a short variable
- is <emphasis role="bold">always</emphasis> large enough to
- hold color intensity values ranging from 0 to 255. Give an
- answer being based on the <link
- xlink:href="https://docs.oracle.com/javase/specs/jls/se8/html/jls-4.html#jls-4.2.1">specification</link>
- and not just by try-and-error.</para>
-
- <para>The programmer tries to adopt the <link
- linkend="sw1QandaMaxMinInt">related int example</link>
- accordingly:</para>
-
- <programlisting language="java">short minumum = 0B10000000_00000000,
- maximum = 0B01111111_11111111;
-System.out.println("Minimum short value:" + minumum);
-System.out.println("Maximum short value:" + maximum);
-</programlisting>
+ <para>This yields:</para>
- <para>Our programmer is baffled since:</para>
+ <screen> Binary:932
+Decimal:932</screen>
+ </listitem>
+
+ <listitem>
+ <para>A negative value in <link xlink:href="https://en.wikipedia.org/wiki/Two's_complement#firstHeading">Two's complement</link> representation starts with a <quote>1</quote> at its highest bit. Binary literals in <xref linkend="glo_Java"/> represent <code>int</code> values. An <code>int</code> in <xref linkend="glo_Java"/> uses 4 bytes and thus occupies 4 x 8=32 bits. Therefore choosing a negative value is a simple task: Start with <quote>1</quote> and let it follow by 32 - 1 = 31 random bit values:</para>
+
+ <programlisting language="java">public static void main(String[] args) {
+ System.out.println(0B10000000_00111001_01101001_01110100);
+}</programlisting>
+ </listitem>
+ </orderedlist>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
+
+ <qandaset defaultlabel="qanda" xml:id="sd1QandaBracesInPrintln">
+ <title>Why using braces inside <code>System.out.println(...)</code> ?</title>
+
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>Solution <xref linkend="sd1QandaBinaryIntLiteral"/> contains:</para>
+
+ <programlisting language="java">...
+System.out.println("Decimal:" + (512 +
+ 256 +
+ 128 +
+ 32 +
+ 4)); ...</programlisting>
+ <para>Why are the <quote>inner</quote> braces immediately preceding 512 and following 4 are being required?</para>
+
+ <tip>
<itemizedlist>
<listitem>
- <para>The first assignment <code language="java">minumum =
- 0B10000000_00000000</code> is being flagged as a compile
- time error:</para>
-
- <para><computeroutput>Type mismatch: cannot convert from
- int to short</computeroutput></para>
+ <para>Execute the above code omitting the <quote>inner</quote> braces.</para>
</listitem>
<listitem>
- <para>On contrary the second assignment <code
- language="java">maximum = 0B01111111_11111111</code> gets
- smoothly accepted.</para>
+ <para>Read about the <quote>+</quote> operator's role e.g. in <code>System.out.println("Some" + " string").</code></para>
</listitem>
</itemizedlist>
+ </tip>
+ </question>
- <tip>
- <para>Which integer literals types do exist according to the
- <xref linkend="glo_Java"/> <link
- xlink:href="https://docs.oracle.com/javase/specs/jls/se8/html/jls-3.html#jls-3.10.1">standard</link>?</para>
- </tip>
- </question>
-
- <answer>
- <para>Since variables of type <code>short</code> are being
- represented by to bytes their range is <inlineequation>
- <m:math display="inline">
- <m:mrow>
- <m:mo>[</m:mo>
+ <answer>
+ <para>We start omitting the <quote>inner</quote> braces:</para>
- <m:mrow>
- <m:mrow>
- <m:mo>-</m:mo>
+ <programlisting language="java">...
+System.out.println("Decimal:" + 512 +
+ 256 +
+ 128 +
+ 32 +
+ 4); ...</programlisting>
- <m:msup>
- <m:mi>2</m:mi>
+ <para>This results in the following output:</para>
- <m:mi>15</m:mi>
- </m:msup>
- </m:mrow>
+ <screen>...
+Decimal:512256128324</screen>
- <m:mo>,</m:mo>
+ <para>The numbers are being treated as strings rather than integer values The above code is equivalent to:</para>
- <m:mrow>
- <m:msup>
- <m:mi>2</m:mi>
+ <programlisting language="java">...
+System.out.println("Decimal:" + "512" +
+ "256" +
+ "128" +
+ "32" +
+ "4"); ...</programlisting>
- <m:mi>15</m:mi>
- </m:msup>
+ <para>The <quote>+</quote> operator between two strings defines their concatenation. So all six components get joined into a single result string.</para>
- <m:mo>-</m:mo>
+ <para>Supplying additional inner braces defines an expression (512 + 256 + 128 + 32 + 4) solely involving integer values. In this context each <quote>+</quote> operator effects the usual integer arithmetic:</para>
- <m:mi>1</m:mi>
- </m:mrow>
- </m:mrow>
+ <programlisting language="java">...
+System.out.println("Decimal:" +<co linkends="sd1ListingPlusOpDuplicate-1" xml:id="sd1ListingPlusOpDuplicate-1-co"/> (512 +<co linkends="sd1ListingPlusOpDuplicate-2" xml:id="sd1ListingPlusOpDuplicate-2-co"/>
+ 256 +<co linkends="sd1ListingPlusOpDuplicate-2" xml:id="sd1ListingPlusOpDuplicate-3-co"/>
+ 128 +<co linkends="sd1ListingPlusOpDuplicate-2" xml:id="sd1ListingPlusOpDuplicate-4-co"/>
+ 32 +<co linkends="sd1ListingPlusOpDuplicate-2" xml:id="sd1ListingPlusOpDuplicate-5-co"/>
+ 4)); ...</programlisting>
- <m:mo>]</m:mo>
- </m:mrow>
- </m:math>
- </inlineequation>. Thus intensity values ranging from 0 to
- 255 will be easily accommodated.</para>
-
- <para>The second question is more difficult to explain: The
- <xref linkend="glo_Java"/> standard does define
- <code>int</code> literals. It does however not define
- <code>short</code> (or <code>byte</code>) literals.</para>
-
- <para>Thus the 0B01111111_11111111 literal will be treated as
- an <code>int</code> value being compatible with a
- <code>short</code> variable and is thus assignable.</para>
-
- <para>On the contrary the binary value
- <code>10000000_00000000</code> evaluates to <inlineequation>
- <m:math display="inline">
- <m:msup>
- <m:mn>2</m:mn>
+ <calloutlist>
+ <callout arearefs="sd1ListingPlusOpDuplicate-1-co" xml:id="sd1ListingPlusOpDuplicate-1">
+ <para><quote>+</quote> operator concatenating the two strings <code>"Decimal:"</code> and <code>"932"</code>.</para>
+ </callout>
- <m:mi>15</m:mi>
- </m:msup>
- </m:math>
- </inlineequation> (equal to 32768) exceeding a two-byte
- short variable's upper limit.</para>
-
- <para>Even worse: A <code>short</code> variable containing
- binary <code>10000000_00000000</code> due to its two byte
- <link
- xlink:href="https://en.wikipedia.org/wiki/Two's_complement#firstHeading">Two's
- complement</link> representation has got a value
- <inlineequation>
- <m:math display="inline">
- <m:mrow>
- <m:mo>-</m:mo>
+ <callout arearefs="sd1ListingPlusOpDuplicate-2-co sd1ListingPlusOpDuplicate-3-co sd1ListingPlusOpDuplicate-4-co sd1ListingPlusOpDuplicate-5-co" xml:id="sd1ListingPlusOpDuplicate-2">
+ <para><quote>+</quote> operators computing the integer sum of 512, 256, 128, 32 and 4 yielding a value of 932. This value subsequently gets transformed into the String <code>"932"</code> in order to be compatible with the preceding <code>"Decimal:"</code> string.</para>
+ </callout>
+ </calloutlist>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
+
+ <qandaset defaultlabel="qanda" xml:id="sd1_qanda_exerciseEmoticons">
+ <title><xref linkend="glo_unicode"/> and emoticons</title>
+
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>Referring to <xref linkend="sd1_fig_unicodeSample"/> we may use a corresponding <link xlink:href="https://en.wikibooks.org/wiki/Java_Programming/Literals#Character_Literals">character literal</link> representing Arabic:</para>
+
+ <programlisting language="java">final char arabicChar = 'ڜ'; // A <link xlink:href="https://en.wikibooks.org/wiki/Java_Programming/Literals#Character_Literals">character literal</link>
+System.out.println("Character: " + arabicChar);</programlisting>
+
+ <para>Execution yields the expected output. On contrary the following code snippet using the smiley instead does not even compile:</para>
+ <mediaobject>
+ <imageobject>
+ <imagedata fileref="Ref/LangFundament/emoticonInvalidCharacterConstant.png"/>
+ </imageobject>
+ </mediaobject>
+
+ <para>Explain the underlying problem.</para>
+
+ <tip>
+ <para>Consider the number of bytes being allocated for <code>char</code> values in <xref linkend="glo_Java"/>.</para>
+ </tip>
+ </question>
+
+ <answer>
+ <para>According to the <link xlink:href="https://en.wikipedia.org/wiki/Arabic_(Unicode_block)#Block">Arabic block</link> table the code point of <code>'ڜ'</code> is U+069C having a decimal equivalent of 1692.</para>
+
+ <para><xref linkend="glo_Java"/> uses two bytes equivalent to 16 bits for representing positive <code>char</code> values. Thus the largest representable code point value is <inlineequation>
+ <m:math display="inline">
+ <m:mrow>
+ <m:mrow>
<m:msup>
- <m:mn>2</m:mn>
+ <m:mi>2</m:mi>
- <m:mi>15</m:mi>
+ <m:mi>16</m:mi>
</m:msup>
- </m:mrow>
- </m:math>
- </inlineequation> (or -32768).</para>
- <para>In order to avoid this error we need an explicit type
- conversion (a so called cast):</para>
+ <m:mo>-</m:mo>
- <programlisting language="java">short minumum = (short) 0B10000000_00000000;</programlisting>
+ <m:mi>1</m:mi>
+ </m:mrow>
- <para>Since a <code>short</code> variable's range is
- <inlineequation>
- <m:math display="inline">
- <m:mrow>
- <m:mo>[</m:mo>
+ <m:mo>=</m:mo>
- <m:mrow>
- <m:mrow>
- <m:mo>-</m:mo>
+ <m:mi>65535</m:mi>
+ </m:mrow>
+ </m:math>
+ </inlineequation>. So <code>'ڜ'</code> fits well into this range.</para>
- <m:msup>
- <m:mi>2</m:mi>
+ <para>According to the <link xlink:href="https://en.wikipedia.org/wiki/Emoticons_(Unicode_block)">Emoticons table</link> the smiley's code point value is U+1F60E being equivalent to 128526 decimal. This exceeds the limit of 65535 and thus prohibits the character literal in question.</para>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
+ </section>
- <m:mi>15</m:mi>
- </m:msup>
- </m:mrow>
+ <section xml:id="sd1_sect_arithmeticLimitations">
+ <title>Arithmetic limitations</title>
- <m:mo>,</m:mo>
+ <para>Expect the unexpected:</para>
- <m:mrow>
- <m:msup>
- <m:mi>2</m:mi>
+ <figure xml:id="sd1_fig_byteLitteralAssign">
+ <title>Strange things</title>
- <m:mi>15</m:mi>
- </m:msup>
+ <programlisting language="java">byte count = 91; // o.K.
- <m:mo>-</m:mo>
+byte points = 130; // Compile error: Incompatible types
+ // Required: byte Found: int</programlisting>
+ </figure>
- <m:mi>1</m:mi>
- </m:mrow>
- </m:mrow>
+ <figure xml:id="sd1_fig_byteOverflow">
+ <title>Overflow</title>
- <m:mo>]</m:mo>
- </m:mrow>
- </m:math>
- </inlineequation> we may as well use a unary minus sign
- instead:</para>
+ <programlisting language="java">int count = 2147483647;
+int points = 2147483647;
- <programlisting language="java">short minumum = -0B10000000_00000000;</programlisting>
+int sum = count + points;
+System.out.println("Sum = " + sum);</programlisting>
- <para>Both variants are syntactically correct and will thus
- compile. However they are likely not being intended by our
- programmer.</para>
+ <para>Result:</para>
- <para>The error in the first place is probably assigning a
- value of <inlineequation>
- <m:math display="inline">
- <m:mrow>
- <m:mo>+</m:mo>
+ <informaltable border="1">
+ <tr>
+ <td valign="top"><screen>Sum = -2</screen></td>
- <m:msup>
- <m:mi>2</m:mi>
+ <td><screen> 01111111_11111111_11111111_11111111
++ 01111111_11111111_11111111_11111111
+_____________________________________
+ 11111111_11111111_11111111_11111110</screen></td>
+ </tr>
+ </informaltable>
+ </figure>
- <m:mi>15</m:mi>
- </m:msup>
- </m:mrow>
- </m:math>
- </inlineequation> to a <code>short</code> variable at
- all.</para>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
- </section>
+ <para>Why not using float / double in favour of bounded <code>byte</code>, <code>short</code>, <code>int</code>, <code>long</code> for arithmetics?</para>
- <section xml:id="sd1_sect_exerciseEmoticons">
- <title><xref linkend="glo_unicode"/> and emoticons</title>
+ <figure xml:id="sd1_fig_floatPrecision">
+ <title>Limited precision</title>
- <qandaset defaultlabel="qanda" xml:id="sd1_qanda_exerciseEmoticons">
- <qandadiv>
- <qandaentry>
- <question>
- <para>Referring to <xref linkend="sd1_fig_unicodeSample"/> we
- may use a corresponding <link
- xlink:href="https://en.wikibooks.org/wiki/Java_Programming/Literals#Character_Literals">character
- literal</link>:</para>
-
- <programlisting language="java">final char arabicChar = 'ڜ'; // A <link
- xlink:href="https://en.wikibooks.org/wiki/Java_Programming/Literals#Character_Literals">character literal</link>
-System.out.println("Character: " + arabicChar);</programlisting>
+ <programlisting language="java">float float2Power31 = Integer.MAX_VALUE + 1f;
- <para>Execution yields the expected output. On contrary the
- following code snippet using the smiley instead does not even
- compile:</para>
-
- <mediaobject>
- <imageobject>
- <imagedata fileref="Ref/LangFundament/emoticonInvalidCharacterConstant.png"/>
- </imageobject>
- </mediaobject>
-
- <para>Explain the underlying problem.</para>
-
- <tip>
- <para>Consider the number of bytes being allocated for
- <code>char</code> values in <xref
- linkend="glo_Java"/>.</para>
- </tip>
- </question>
-
- <answer>
- <para>According to the <link
- xlink:href="https://en.wikipedia.org/wiki/Arabic_(Unicode_block)#Block">Arabic
- block</link> table the code point of <code>'ڜ'</code> is
- U+069C having a decimal equivalent of 1692.</para>
-
- <para><xref linkend="glo_Java"/> uses two bytes equivalent to
- 16 bits for representing positive <code>char</code> values.
- Thus the largest representable code point value is
- <inlineequation>
- <m:math display="inline">
- <m:mrow>
- <m:mrow>
- <m:msup>
- <m:mi>2</m:mi>
+float floatDoubleMAX_VALUE = 2 * float2Power31* float2Power31 - 1f; // 2^63 - 1
- <m:mi>16</m:mi>
- </m:msup>
+System.out.format( " Float value: %f\n", floatDoubleMAX_VALUE);
+System.out.println("Expected value: " + Long.MAX_VALUE);</programlisting>
- <m:mo>-</m:mo>
+ <para>Result:</para>
- <m:mi>1</m:mi>
- </m:mrow>
+ <screen> Float value: 9223372036854776000.000000
+Expected value: 9223372036854775807</screen>
+ </figure>
- <m:mo>=</m:mo>
+ <figure xml:id="sd1_fig_floatConverter">
+ <title><uri xlink:href="https://www.h-schmidt.net/FloatConverter">https://www.h-schmidt.net/FloatConverter</uri></title>
- <m:mi>65535</m:mi>
- </m:mrow>
- </m:math>
- </inlineequation>. So <code>'ڜ'</code> fits well into this
- range.</para>
-
- <para>According to the <link
- xlink:href="https://en.wikipedia.org/wiki/Emoticons_(Unicode_block)">Emoticons
- table</link> the smiley's code point value is U+1F60E being
- equivalent to 128526 decimal. This exceeds the limit of 65535
- and thus prohibits the character literal in question.</para>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
- </section>
+ <mediaobject>
+ <imageobject>
+ <imagedata fileref="Ref/LangFundament/floatConverter.png"/>
+ </imageobject>
+ </mediaobject>
+ </figure>
+ </section>
+ </section>
- <section xml:id="sd1SectIntMinMax">
- <title>An <code>int</code>'s minimum and maximum value</title>
+ <section xml:id="sd1_sect_langFundamental_exercises">
+ <title>Exercises</title>
- <qandaset defaultlabel="qanda" xml:id="sw1QandaMaxMinInt">
- <qandadiv>
- <qandaentry>
- <question>
- <para>In this exercise we look at an <code>int</code>'s the
- largest and smallest possible value.</para>
-
- <para>A <xref linkend="glo_Java"/> <code
- xlink:href="https://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html">int</code>
- is internally being represented by 4 <link
- linkend="glo_byte">bytes</link>. <inlineequation>
- <m:math display="inline">
- <m:msub>
- <m:mi>00000000000000000000000000000101</m:mi>
+ <section xml:id="sw1SectSimpleExpressions">
+ <title>Simple expressions</title>
- <m:mi>2</m:mi>
- </m:msub>
- </m:math>
- </inlineequation> for example represents the decimal value
- 5.</para>
+ <qandaset defaultlabel="qanda" xml:id="sw1QandaGuessingResults">
+ <title>Guessing results</title>
- <para>In order to represent negative values as well <xref
- linkend="glo_Java"/> uses <link
- xlink:href="https://en.wikipedia.org/wiki/Two's_complement#firstHeading">Two's
- complement</link> representation. We provide some
- values:</para>
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>Consider the following code segment:</para>
- <table border="1" xml:id="sw1Table4ByteIntegerRepresentation">
- <caption>4 Byte <link
- xlink:href="https://en.wikipedia.org/wiki/Two's_complement#firstHeading">Two's
- complement</link> representation of <code>int</code>
- values.</caption>
+ <programlisting language="java"> int a = 3;
+ a++; //Incrementing a by 1 --> a==4
- <tr>
- <th>Two complement representation</th>
+ int b = a; // TODO
- <th>Decimal representation</th>
- </tr>
+ b--; // TODO
+ --b; // TODO
- <tr>
- <td><code>00000000000000000000000000000000</code></td>
+ int c = b; // TODO
- <td>0</td>
- </tr>
+ b = ++a; // TODO
+ int e = a++; // TODO
- <tr>
- <td><code>01111111111111111111111111111111</code></td>
+ a *= b; // TODO
- <td><inlineequation>
- <m:math display="inline">
- <m:mrow>
- <m:msup>
- <m:mi>2</m:mi>
+ System.out.println("a=" + a);
+ System.out.println("b=" + b);
+ System.out.println("c=" + c);
+ System.out.println("e=" + e);</programlisting>
- <m:mrow>
- <m:mi>16</m:mi>
+ <para>We want to guess the expected result. Copy/paste the above code into a main() method body within your IDE of choice (probably Eclipse).</para>
- <m:mo>-</m:mo>
+ <para><emphasis role="bold">Do not execute this code yet</emphasis> but replace the TODO comments by guessing the respective variable's value.</para>
- <m:mi>1</m:mi>
- </m:mrow>
- </m:msup>
+ <para><computeroutput>a=...</computeroutput></para>
- <m:mo>-</m:mo>
+ <para><computeroutput>b=...</computeroutput></para>
- <m:mi>1</m:mi>
- </m:mrow>
- </m:math>
- </inlineequation> (Maximum)</td>
- </tr>
+ <para><computeroutput>c=...</computeroutput></para>
- <tr>
- <td><code>10000000000000000000000000000000</code></td>
+ <para><computeroutput>e=...</computeroutput></para>
- <td><inlineequation>
- <m:math display="inline">
- <m:mrow>
- <m:mo>-</m:mo>
+ <para>After finishing your guesses execute your code and start wailing about your success rate.</para>
- <m:msup>
- <m:mi>2</m:mi>
+ <tip>
+ <para>Both <code>x++</code> (postfix notation) and <code>++x</code> (infix notation) are expressions themselves which might even be rewritten as <code>(x++)</code> and <code>(++x)</code> for the sake of clarity. The difference is not about operator precedence rules but simply about the values of these expressions when being assigned to other variables.</para>
+ </tip>
+ </question>
- <m:mrow>
- <m:mi>16</m:mi>
+ <answer>
+ <para>As inferred by the hint the biggest problem is about understanding postfix and infix notation of the operators <code>++</code> and <code>--</code>. A corresponding expression evaluates to:</para>
- <m:mo>-</m:mo>
+ <itemizedlist>
+ <listitem>
+ <para><code>a = x++</code> yields a ==x</para>
+ </listitem>
- <m:mi>1</m:mi>
- </m:mrow>
- </m:msup>
- </m:mrow>
- </m:math>
- </inlineequation> (Minimum)</td>
- </tr>
-
- <tr>
- <td><code>11111111111111111111111111111111</code></td>
-
- <td>-1</td>
- </tr>
- </table>
-
- <para>Use <link
- xlink:href="https://docs.oracle.com/javase/specs/jls/se8/html/jls-3.html#jls-3.10.1"><code>int</code>
- literals</link> in <link
- xlink:href="https://docs.oracle.com/javase/specs/jls/se8/html/jls-3.html#jls-BinaryNumeral">binary
- representation</link> like e.g. <code>0B1100</code> in section
- <quote
- xlink:href="https://proquest.safaribooksonline.com/9780992133047/toc6_html_2">Literals</quote>
- in order to write an <code>int</code>'s minimum and maximum
- possible value to standard output.</para>
-
- <programlisting language="java"> public static void main(String[] args) {
-
- int minumum = ... , //TODO: provide values by
- maximum = ...; // binary int literals
+ <listitem>
+ <para><code>a = ++x</code> yields a ==(x + 1)</para>
+ </listitem>
+ </itemizedlist>
- System.out.println("Minimum:" + minumum);
- System.out.println("Maximum:" + maximum);
- }</programlisting>
- </question>
+ <para>The rest is just obeying the <quote>due diligence</quote> rule set:</para>
- <answer>
- <para>We insert <link
- xlink:href="https://en.wikipedia.org/wiki/Two's_complement#firstHeading">Two's
- complement</link> representations of minimum and maximum int
- values according to <xref
- linkend="sw1Table4ByteIntegerRepresentation"/>.</para>
+ <programlisting language="java"> int a = 3;
+ a++; //Incrementing a by 1 --> a==4
- <programlisting language="java">public static void main(String[] args) {
-
- int minumum = 0B10000000_00000000_00000000_00000000,
- maximum = 0B01111111_11111111_11111111_11111111;
+ int b = a; // Assigning value of a --> b==4
- System.out.println("Minimum int value:" + minumum);
- System.out.println("Maximum int value:" + maximum);
- }</programlisting>
+ b--; // Decrementing b by 1 --> b==3
+ --b; // Decrementing b by 1 --> b==2
- <para>BTW: The <xref linkend="glo_JDK"/> does provide maximum
- value, minimum value and related information for
- <code>char</code>, <code>byte</code>, <code>short</code> and
- <code>int</code> data types int its related <classname
- xlink:href="https://docs.oracle.com/javase/8/docs/api/java/lang/Character.html">Character</classname>,
- <classname
- xlink:href="https://docs.oracle.com/javase/8/docs/api/java/lang/Byte.html">Byte</classname>,
- <classname
- xlink:href="https://docs.oracle.com/javase/8/docs/api/java/lang/Short.html">Short</classname>
- and <classname
- xlink:href="https://docs.oracle.com/javase/8/docs/api/java/lang/Integer.html">Integer</classname>
- classes. You may want to execute:</para>
-
- <programlisting language="java"> System.out.println("int minimum:" + Integer.MIN_VALUE);
- System.out.println("int minimum:" + Integer.MAX_VALUE);
-
- System.out.println("int bytes:" + Integer.BYTES);
- System.out.println("int size:" + Integer.SIZE);
-</programlisting>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
- </section>
+ int c = b; // c == 2;
- <section xml:id="sd1_sect_literalProblem">
- <title>Literal problem</title>
+ b = ++a; // Incrementing a by 1 -->a==5, then assigning to b --> b == 5
+ int e = a++; // Assigning a to e --> e==5, then incrementing a --> a==6
- <qandaset defaultlabel="qanda" xml:id="sd1_qanda_literalProblem">
- <qandadiv>
- <qandaentry>
- <question>
- <para>Consider:</para>
-
- <programlisting language="java">System.out.println(048);</programlisting>
-
- <para>This yields a compile time error <quote>Integer number
- too large</quote>. On contrary the following code will compile
- and run perfectly well:</para>
-
- <programlisting language="java">System.out.println(047);</programlisting>
-
- <para>Explain the underlying problem.</para>
- </question>
-
- <answer>
- <para>The literal <quote>048</quote> is meant to be octal
- representation. Unfortunately the only digits in octal
- representations range from 0 to 7. So <quote>047</quote> is
- fine but <quote>048</quote> simply is no valid literal in
- <xref linkend="glo_Java"/>.</para>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
- </section>
- </section>
+ a *= b; // Multiplying a with b and assigning the result to a --> a==30
- <section xml:id="sw1SectSimpleExpressions">
- <title>Simple expressions</title>
+ System.out.println("a=" + a);
+ System.out.println("b=" + b);
+ System.out.println("c=" + c);
+ System.out.println("e=" + e);</programlisting>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
- <section xml:id="sd1SectCircleArea">
+ <qandaset defaultlabel="qanda" xml:id="sw1QandaCircleArea">
<title>Calculating a circle area</title>
- <qandaset defaultlabel="qanda" xml:id="sw1QandaCircleArea">
- <qandadiv>
- <qandaentry>
- <question>
- <para>The area <inlineequation>
- <m:math display="inline">
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>The area <inlineequation>
+ <m:math display="inline">
+ <m:mi>a</m:mi>
+ </m:math>
+ </inlineequation> of a given circle having radius <inlineequation>
+ <m:math display="inline">
+ <m:mi>r</m:mi>
+ </m:math>
+ </inlineequation> is being obtained by <inlineequation>
+ <m:math display="inline">
+ <m:mrow>
<m:mi>a</m:mi>
- </m:math>
- </inlineequation> of a given circle having radius
- <inlineequation>
- <m:math display="inline">
- <m:mi>r</m:mi>
- </m:math>
- </inlineequation> is being obtained by <inlineequation>
- <m:math display="inline">
- <m:mrow>
- <m:mi>a</m:mi>
- <m:mo>=</m:mo>
+ <m:mo>=</m:mo>
- <m:mrow>
- <m:mi>Ï€</m:mi>
+ <m:mrow>
+ <m:mi>Ï€</m:mi>
- <m:mo>×</m:mo>
+ <m:mo>×</m:mo>
- <m:msup>
- <m:mi>r</m:mi>
+ <m:msup>
+ <m:mi>r</m:mi>
- <m:mi>2</m:mi>
- </m:msup>
- </m:mrow>
+ <m:mi>2</m:mi>
+ </m:msup>
</m:mrow>
- </m:math>
- </inlineequation>. Complete the following code to calculate
- the result and write it to standard output using
- <code>System.out.println(...)</code>:</para>
+ </m:mrow>
+ </m:math>
+ </inlineequation>. Complete the following code to calculate the result and write it to standard output using <code>System.out.println(...)</code>:</para>
- <programlisting language="java">public static void main(String[] args) {
+ <programlisting language="java">public static void main(String[] args) {
double radius = 2.31; // A circle having a radius (given e.g. in mm).
double pi = 3.1415926; // Constant relating a circle's radius,
@@ -2101,20 +1890,18 @@ System.out.println("Character: " + arabicChar);</programlisting>
// TODO: Write the circle's area to standard output
}</programlisting>
- <tip>
- <para>You may want to read the <link
- xlink:href="https://proquest.safaribooksonline.com/9780992133047/toc1_html_4">overview
- section</link> on statements.</para>
- </tip>
- </question>
+ <tip>
+ <para>You may want to read the <link xlink:href="https://proquest.safaribooksonline.com/9780992133047/toc1_html_4">overview section</link> on statements.</para>
+ </tip>
+ </question>
- <answer>
- <glosslist>
- <glossentry>
- <glossterm>Using a mere expression</glossterm>
+ <answer>
+ <glosslist>
+ <glossentry>
+ <glossterm>Using a mere expression</glossterm>
- <glossdef>
- <programlisting language="java">public static void main(String[] args) {
+ <glossdef>
+ <programlisting language="java">public static void main(String[] args) {
double radius = 2.31; // A circle having a radius (given e.g. in mm).
double pi = 3.1415926; // Constant relating a circle's radius,
@@ -2122,19 +1909,16 @@ System.out.println("Character: " + arabicChar);</programlisting>
System.out.println(pi * radius * radius);
}</programlisting>
- </glossdef>
- </glossentry>
+ </glossdef>
+ </glossentry>
- <glossentry>
- <glossterm>Using a variable</glossterm>
+ <glossentry>
+ <glossterm>Using a variable</glossterm>
- <glossdef>
- <para>Instead of immediately using the expression as an
- argument to <code>System.out.println(...)</code> we may
- assign its value to a variable prior to output
- creation:</para>
+ <glossdef>
+ <para>Instead of immediately using the expression as an argument to <code>System.out.println(...)</code> we may assign its value to a variable prior to output creation:</para>
- <programlisting language="java">public static void main(String[] args) {
+ <programlisting language="java">public static void main(String[] args) {
double radius = 2.31; // A circle having a radius (given e.g. in mm).
double pi = 3.1415926; // Constant relating a circle's radius,
@@ -2143,27 +1927,23 @@ System.out.println("Character: " + arabicChar);</programlisting>
double area = pi * radius * radius;
System.out.println(area);
}</programlisting>
- </glossdef>
- </glossentry>
- </glosslist>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
- </section>
+ </glossdef>
+ </glossentry>
+ </glosslist>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
- <section xml:id="sd1SectTemperatureConvert">
+ <qandaset defaultlabel="qanda" xml:id="sd1QandaTemperatureConvert">
<title>Converting temperature values</title>
- <qandaset defaultlabel="qanda" xml:id="sd1QandaTemperatureConvert">
- <qandadiv>
- <qandaentry>
- <question>
- <para>Write an application converting temperature values being
- represented as degree centigrade to kelvin and
- Fahrenheit:</para>
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>Write an application converting temperature values being represented as degree centigrade to kelvin and Fahrenheit:</para>
- <programlisting language="java"> public static void main(String[] args) {
+ <programlisting language="java"> public static void main(String[] args) {
double temperatureCelsius = 23.2;
@@ -2173,10 +1953,10 @@ System.out.println("Character: " + arabicChar);</programlisting>
System.out.println("Kelvin: " + temperatureKelvin);
System.out.println("Fahrenheit: " + temperatureFahrenheit);
}</programlisting>
- </question>
+ </question>
- <answer>
- <programlisting language="java"> public static void main(String[] args) {
+ <answer>
+ <programlisting language="java"> public static void main(String[] args) {
double temperatureCelsius = 23.2;
@@ -2188,27 +1968,24 @@ System.out.println("Character: " + arabicChar);</programlisting>
System.out.println("Kelvin: " + temperatureKelvin);
System.out.println("Fahrenheit: " + temperatureFahrenheit);
}</programlisting>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
- </section>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
- <section xml:id="sd1SectTimeUnits">
+ <qandaset defaultlabel="qanda" xml:id="sd1QandaTimeUnits">
<title>Time unit conversion</title>
- <qandaset defaultlabel="qanda" xml:id="sd1QandaTimeUnits">
- <qandadiv>
- <qandaentry>
- <question>
- <para>This exercise consists of two parts:</para>
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>This exercise consists of two parts:</para>
- <orderedlist>
- <listitem>
- <para>Write an application converting a (seconds, minutes
- ,hours) time specification to seconds:</para>
+ <orderedlist>
+ <listitem>
+ <para>Write an application converting a (seconds, minutes ,hours) time specification to seconds:</para>
- <programlisting language="java"> public static void main(String[] args) {
+ <programlisting language="java"> public static void main(String[] args) {
final int
seconds = 31,
@@ -2220,17 +1997,15 @@ System.out.println("Character: " + arabicChar);</programlisting>
System.out.println("Time in seconds:" + timeInSeconds);
}</programlisting>
- <para>The expected output reads:</para>
+ <para>The expected output reads:</para>
- <screen>Time in seconds:15391</screen>
- </listitem>
+ <screen>Time in seconds:15391</screen>
+ </listitem>
- <listitem>
- <para>Reverse the previous part of this exercise: Convert
- a time specification in seconds to (seconds, minutes
- ,hours) as in:</para>
+ <listitem>
+ <para>Reverse the previous part of this exercise: Convert a time specification in seconds to (seconds, minutes ,hours) as in:</para>
- <programlisting language="java"> public static void main(String[] args) {
+ <programlisting language="java"> public static void main(String[] args) {
final int timeInSeconds = 15391;
@@ -2241,28 +2016,25 @@ System.out.println("Character: " + arabicChar);</programlisting>
System.out.println("Seconds:" + seconds);
}</programlisting>
- <para>The expected output reads:</para>
+ <para>The expected output reads:</para>
- <screen>Hours:4
+ <screen>Hours:4
Minutes:16
Seconds:31</screen>
- <tip>
- <para>Consider the <link
- xlink:href="https://docs.oracle.com/javase/tutorial/java/nutsandbolts/op1.html">remainder
- operator <quote>%</quote></link> (modulo
- operator).</para>
- </tip>
- </listitem>
- </orderedlist>
- </question>
+ <tip>
+ <para>Consider the <link xlink:href="https://docs.oracle.com/javase/tutorial/java/nutsandbolts/op1.html">remainder operator <quote>%</quote></link> (modulo operator).</para>
+ </tip>
+ </listitem>
+ </orderedlist>
+ </question>
- <answer>
- <orderedlist>
- <listitem>
- <para>A straightforward solution reads:</para>
+ <answer>
+ <orderedlist>
+ <listitem>
+ <para>A straightforward solution reads:</para>
- <para><programlisting language="java"> public static void main(String[] args) {
+ <para><programlisting language="java"> public static void main(String[] args) {
final int
seconds = 31,
@@ -2273,10 +2045,10 @@ Seconds:31</screen>
System.out.println("Time in seconds:" + timeInSeconds);
}</programlisting></para>
- </listitem>
+ </listitem>
- <listitem>
- <programlisting language="java"> public static void main(String[] args) {
+ <listitem>
+ <programlisting language="java"> public static void main(String[] args) {
final int timeInSeconds = 15391;
@@ -2290,622 +2062,545 @@ Seconds:31</screen>
System.out.println("Minutes:" + minutes);
System.out.println("Seconds:" + seconds);
}</programlisting>
- </listitem>
- </orderedlist>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
- </section>
+ </listitem>
+ </orderedlist>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
- <section xml:id="sd1_sect_typeAssignCompat">
+ <qandaset defaultlabel="qanda" xml:id="sd1_qanda_typeAssignCompat">
<title>Assignment and type safety</title>
- <qandaset defaultlabel="qanda" xml:id="sd1_qanda_typeAssignCompat">
- <qandadiv>
- <qandaentry>
- <question>
- <para>We consider:</para>
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>We consider:</para>
- <programlisting language="java">int i = -21;
+ <programlisting language="java">int i = -21;
double d = i;</programlisting>
- <para>This snippet shows perfectly correct <xref
- linkend="glo_Java"/> code. However <xref
- linkend="sd1_fig_typeSafety"/> suggests we should not be
- allowed to assign an <code>int</code> to a <code>double</code>
- value due to type safety.</para>
+ <para>This snippet shows perfectly correct <xref linkend="glo_Java"/> code. However <xref linkend="sd1_fig_typeSafety"/> suggests we should not be allowed to assign an <code>int</code> to a <code>double</code> value due to type safety.</para>
- <para>Even worse: Swapping types yields a compile time
- error:</para>
+ <para>Even worse: Swapping types yields a compile time error:</para>
- <programlisting language="java">double d = 2.4;
+ <programlisting language="java">double d = 2.4;
int i = d; // Error: Incompatible types</programlisting>
- <para>Why is this? Make an educated guess.</para>
- </question>
-
- <answer>
- <para>The first snippet compiles by using the widening
- conversion: When assigning <code>d = i</code> the <xref
- linkend="glo_Java"/> compiler implicitly converts the
- <code>int</code> into a <code>double</code> value.</para>
-
- <para>Turning a double into an int is more cumbersome: The
- expression <code>i = 3.5</code> could be evaluated by agreeing
- on a specific rounding prescription. But what about i =
- 3457357385783573478955345.45? A <xref linkend="glo_Java"/>
- <code>int</code>'s maximum value is <inlineequation>
- <m:math display="inline">
- <m:mrow>
- <m:msup>
- <m:mi>2</m:mi>
+ <para>Why is this? Make an educated guess.</para>
+ </question>
- <m:mi>31</m:mi>
- </m:msup>
+ <answer>
+ <para>The first snippet compiles by using the widening conversion: When assigning <code>d = i</code> the <xref linkend="glo_Java"/> compiler implicitly converts the <code>int</code> into a <code>double</code> value.</para>
- <m:mo>-</m:mo>
+ <para>Turning a double into an int is more cumbersome: The expression <code>i = 3.5</code> could be evaluated by agreeing on a specific rounding prescription. But what about i = 3457357385783573478955345.45? A <xref linkend="glo_Java"/> <code>int</code>'s maximum value is <inlineequation>
+ <m:math display="inline">
+ <m:mrow>
+ <m:msup>
+ <m:mi>2</m:mi>
- <m:mi>1</m:mi>
- </m:mrow>
- </m:math>
- </inlineequation>exceeding the former <code>double</code>
- value.</para>
+ <m:mi>31</m:mi>
+ </m:msup>
+
+ <m:mo>-</m:mo>
- <para>Conclusion: <xref linkend="glo_Java"/> disallows double
- to int assignments unless using a so called cast (explicit
- type conversion):</para>
+ <m:mi>1</m:mi>
+ </m:mrow>
+ </m:math>
+ </inlineequation>exceeding the former <code>double</code> value.</para>
- <programlisting language="java">double d = 2.4;
+ <para>Conclusion: <xref linkend="glo_Java"/> disallows double to int assignments unless using a so called cast (explicit type conversion):</para>
+
+ <programlisting language="java">double d = 2.4;
int i = (int) d; // Explicit cast double to int</programlisting>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
- </section>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
- <section xml:id="sd1SectLong2Float">
+ <qandaset defaultlabel="qanda" xml:id="sd1QandaLong2Float">
<title>Reducing <code>long</code> to <code>int</code></title>
- <qandaset defaultlabel="qanda" xml:id="sd1QandaLong2Float">
- <qandadiv>
- <qandaentry>
- <question>
- <para>Joe programmer intends to map positive <code>long</code>
- values to <code>int</code> values. This requires scaling down
- <quote>half</quote> the <code>long</code> data type's range
- <inlineequation>
- <m:math display="inline">
- <m:mrow>
- <m:mo>[</m:mo>
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>Joe programmer intends to map positive <code>long</code> values to <code>int</code> values. This requires scaling down <quote>half</quote> the <code>long</code> data type's range <inlineequation>
+ <m:math display="inline">
+ <m:mrow>
+ <m:mo>[</m:mo>
- <m:mrow>
- <m:mn>0</m:mn>
+ <m:mrow>
+ <m:mn>0</m:mn>
- <m:mo>,</m:mo>
+ <m:mo>,</m:mo>
- <m:mrow>
- <m:msup>
- <m:mi>2</m:mi>
+ <m:mrow>
+ <m:msup>
+ <m:mi>2</m:mi>
- <m:mi>63</m:mi>
- </m:msup>
+ <m:mi>63</m:mi>
+ </m:msup>
- <m:mo>-</m:mo>
+ <m:mo>-</m:mo>
- <m:mi>1</m:mi>
- </m:mrow>
+ <m:mi>1</m:mi>
</m:mrow>
-
- <m:mo>]</m:mo>
</m:mrow>
- </m:math>
- </inlineequation> to the <code>int</code>'s range of
- <inlineequation>
- <m:math display="inline">
+
+ <m:mo>]</m:mo>
+ </m:mrow>
+ </m:math>
+ </inlineequation> to the <code>int</code>'s range of <inlineequation>
+ <m:math display="inline">
+ <m:mrow>
+ <m:mo>[</m:mo>
+
<m:mrow>
- <m:mo>[</m:mo>
+ <m:mn>0</m:mn>
+
+ <m:mo>,</m:mo>
<m:mrow>
- <m:mn>0</m:mn>
+ <m:msup>
+ <m:mi>2</m:mi>
- <m:mo>,</m:mo>
+ <m:mi>31</m:mi>
+ </m:msup>
- <m:mrow>
- <m:msup>
- <m:mi>2</m:mi>
+ <m:mo>-</m:mo>
- <m:mi>31</m:mi>
- </m:msup>
+ <m:mi>1</m:mi>
+ </m:mrow>
+ </m:mrow>
- <m:mo>-</m:mo>
+ <m:mo>]</m:mo>
+ </m:mrow>
+ </m:math>
+ </inlineequation>:</para>
- <m:mi>1</m:mi>
- </m:mrow>
- </m:mrow>
+ <informaltable border="1">
+ <colgroup width="25%"/>
- <m:mo>]</m:mo>
- </m:mrow>
- </m:math>
- </inlineequation>:</para>
+ <colgroup width="30%"/>
- <informaltable border="1">
- <colgroup width="25%"/>
+ <colgroup width="15%"/>
- <colgroup width="30%"/>
+ <colgroup width="30%"/>
- <colgroup width="15%"/>
+ <tr>
+ <th colspan="2">From</th>
+
+ <th colspan="2">To</th>
+ </tr>
+
+ <tr>
+ <th><code>long</code></th>
+
+ <th><code>remark</code></th>
- <colgroup width="30%"/>
+ <th><code>int</code></th>
- <tr>
- <th colspan="2">From</th>
+ <th>remark</th>
+ </tr>
- <th colspan="2">To</th>
- </tr>
+ <tr>
+ <td align="right">0</td>
- <tr>
- <th><code>long</code></th>
+ <td align="right"/>
- <th><code>remark</code></th>
+ <td align="right">0</td>
- <th><code>int</code></th>
+ <td align="right"/>
+ </tr>
- <th>remark</th>
- </tr>
+ <tr>
+ <td align="right">1</td>
- <tr>
- <td align="right">0</td>
+ <td align="right"/>
- <td align="right"/>
+ <td align="right">0</td>
- <td align="right">0</td>
+ <td align="right"/>
+ </tr>
- <td align="right"/>
- </tr>
+ <tr>
+ <td align="center" colspan="2">...</td>
- <tr>
- <td align="right">1</td>
+ <td align="right">0</td>
- <td align="right"/>
+ <td align="center">...</td>
+ </tr>
- <td align="right">0</td>
+ <tr>
+ <td align="right">4294967295</td>
- <td align="right"/>
- </tr>
+ <td align="right"><inlineequation>
+ <m:math display="inline">
+ <m:mrow>
+ <m:msup>
+ <m:mi>2</m:mi>
- <tr>
- <td align="center" colspan="2">...</td>
+ <m:mi>32</m:mi>
+ </m:msup>
- <td align="right">0</td>
+ <m:mo>-</m:mo>
- <td align="center">...</td>
- </tr>
+ <m:mi>1</m:mi>
+ </m:mrow>
+ </m:math>
+ </inlineequation></td>
- <tr>
- <td align="right">4294967295</td>
+ <td align="right">0</td>
- <td align="right"><inlineequation>
- <m:math display="inline">
- <m:mrow>
- <m:msup>
- <m:mi>2</m:mi>
+ <td align="right"/>
+ </tr>
- <m:mi>32</m:mi>
- </m:msup>
+ <tr>
+ <td align="right">4294967296</td>
- <m:mo>-</m:mo>
+ <td align="right"><inlineequation>
+ <m:math display="inline">
+ <m:msup>
+ <m:mi>2</m:mi>
- <m:mi>1</m:mi>
- </m:mrow>
- </m:math>
- </inlineequation></td>
+ <m:mi>32</m:mi>
+ </m:msup>
+ </m:math>
+ </inlineequation></td>
- <td align="right">0</td>
+ <td align="right">1</td>
- <td align="right"/>
- </tr>
+ <td align="right"/>
+ </tr>
- <tr>
- <td align="right">4294967296</td>
+ <tr>
+ <td align="right">4294967297</td>
- <td align="right"><inlineequation>
- <m:math display="inline">
+ <td align="right"><inlineequation>
+ <m:math display="inline">
+ <m:mrow>
<m:msup>
<m:mi>2</m:mi>
<m:mi>32</m:mi>
</m:msup>
- </m:math>
- </inlineequation></td>
-
- <td align="right">1</td>
-
- <td align="right"/>
- </tr>
- <tr>
- <td align="right">4294967297</td>
+ <m:mo>+</m:mo>
- <td align="right"><inlineequation>
- <m:math display="inline">
- <m:mrow>
- <m:msup>
- <m:mi>2</m:mi>
-
- <m:mi>32</m:mi>
- </m:msup>
+ <m:mi>1</m:mi>
+ </m:mrow>
+ </m:math>
+ </inlineequation></td>
- <m:mo>+</m:mo>
+ <td align="right">1</td>
- <m:mi>1</m:mi>
- </m:mrow>
- </m:math>
- </inlineequation></td>
+ <td align="right"/>
+ </tr>
- <td align="right">1</td>
+ <tr>
+ <td align="center" colspan="4">...</td>
+ </tr>
- <td align="right"/>
- </tr>
+ <tr>
+ <td align="right">9223372036854775806</td>
- <tr>
- <td align="center" colspan="4">...</td>
- </tr>
+ <td align="right"><inlineequation>
+ <m:math display="inline">
+ <m:mrow>
+ <m:msup>
+ <m:mi>2</m:mi>
- <tr>
- <td align="right">9223372036854775806</td>
+ <m:mi>63</m:mi>
+ </m:msup>
- <td align="right"><inlineequation>
- <m:math display="inline">
- <m:mrow>
- <m:msup>
- <m:mi>2</m:mi>
+ <m:mo>-</m:mo>
- <m:mi>63</m:mi>
- </m:msup>
+ <m:mi>2</m:mi>
+ </m:mrow>
+ </m:math>
+ </inlineequation> or <code xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Long.MAX_VALUE"><varname xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Long.MAX_VALUE">Long.MAX_VALUE</varname></code> - 1</td>
- <m:mo>-</m:mo>
+ <td align="right">2147483647</td>
+ <td align="right"><inlineequation>
+ <m:math display="inline">
+ <m:mrow>
+ <m:msup>
<m:mi>2</m:mi>
- </m:mrow>
- </m:math>
- </inlineequation> or <code
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Long.MAX_VALUE"><varname
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Long.MAX_VALUE">Long.MAX_VALUE</varname></code>
- - 1</td>
- <td align="right">2147483647</td>
+ <m:mi>31</m:mi>
+ </m:msup>
- <td align="right"><inlineequation>
- <m:math display="inline">
- <m:mrow>
- <m:msup>
- <m:mi>2</m:mi>
+ <m:mo>-</m:mo>
- <m:mi>31</m:mi>
- </m:msup>
+ <m:mi>1</m:mi>
+ </m:mrow>
+ </m:math>
+ </inlineequation> or <varname xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Integer.MAX_VALUE">Integer.MAX_VALUE</varname></td>
+ </tr>
- <m:mo>-</m:mo>
+ <tr>
+ <td align="right">9223372036854775807</td>
- <m:mi>1</m:mi>
- </m:mrow>
- </m:math>
- </inlineequation> or <varname
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Integer.MAX_VALUE">Integer.MAX_VALUE</varname></td>
- </tr>
+ <td align="right"><inlineequation>
+ <m:math display="inline">
+ <m:mrow>
+ <m:msup>
+ <m:mi>2</m:mi>
+
+ <m:mi>63</m:mi>
+ </m:msup>
- <tr>
- <td align="right">9223372036854775807</td>
+ <m:mo>-</m:mo>
- <td align="right"><inlineequation>
- <m:math display="inline">
- <m:mrow>
- <m:msup>
- <m:mi>2</m:mi>
+ <m:mi>1</m:mi>
+ </m:mrow>
+ </m:math>
+ </inlineequation> or <varname xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Long.MAX_VALUE">Long.MAX_VALUE</varname></td>
- <m:mi>63</m:mi>
- </m:msup>
+ <td align="right">2147483647</td>
- <m:mo>-</m:mo>
+ <td align="right"><inlineequation>
+ <m:math display="inline">
+ <m:mrow>
+ <m:msup>
+ <m:mi>2</m:mi>
- <m:mi>1</m:mi>
- </m:mrow>
- </m:math>
- </inlineequation> or <varname
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Long.MAX_VALUE">Long.MAX_VALUE</varname></td>
+ <m:mi>31</m:mi>
+ </m:msup>
- <td align="right">2147483647</td>
+ <m:mo>-</m:mo>
- <td align="right"><inlineequation>
- <m:math display="inline">
- <m:mrow>
- <m:msup>
- <m:mi>2</m:mi>
+ <m:mi>1</m:mi>
+ </m:mrow>
+ </m:math>
+ </inlineequation> or <varname xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Integer.MAX_VALUE">Integer.MAX_VALUE</varname></td>
+ </tr>
+ </informaltable>
- <m:mi>31</m:mi>
- </m:msup>
+ <para>Joe's idea is dividing <code>long</code> values by <inlineequation>
+ <m:math display="inline">
+ <m:msup>
+ <m:mi>2</m:mi>
- <m:mo>-</m:mo>
+ <m:mi>32</m:mi>
+ </m:msup>
+ </m:math>
+ </inlineequation>. As a result a long value of <inlineequation>
+ <m:math display="inline">
+ <m:mrow>
+ <m:mo>-</m:mo>
- <m:mi>1</m:mi>
- </m:mrow>
- </m:math>
- </inlineequation> or <varname
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Integer.MAX_VALUE">Integer.MAX_VALUE</varname></td>
- </tr>
- </informaltable>
-
- <para>Joe's idea is dividing <code>long</code> values by
- <inlineequation>
- <m:math display="inline">
<m:msup>
<m:mi>2</m:mi>
- <m:mi>32</m:mi>
+ <m:mi>63</m:mi>
</m:msup>
- </m:math>
- </inlineequation>. As a result a long value of
- <inlineequation>
- <m:math display="inline">
- <m:mrow>
- <m:mo>-</m:mo>
-
- <m:msup>
- <m:mi>2</m:mi>
-
- <m:mi>63</m:mi>
- </m:msup>
- </m:mrow>
- </m:math>
- </inlineequation> will be reduced to the intended value of
- <inlineequation>
- <m:math display="inline">
- <m:mrow>
- <m:mo>-</m:mo>
-
- <m:msup>
- <m:mi>2</m:mi>
+ </m:mrow>
+ </m:math>
+ </inlineequation> will be reduced to the intended value of <inlineequation>
+ <m:math display="inline">
+ <m:mrow>
+ <m:mo>-</m:mo>
- <m:mi>31</m:mi>
- </m:msup>
- </m:mrow>
- </m:math>
- </inlineequation>. Since <inlineequation>
- <m:math display="inline">
<m:msup>
<m:mi>2</m:mi>
- <m:mi>32</m:mi>
+ <m:mi>31</m:mi>
</m:msup>
- </m:math>
- </inlineequation> seems to be equal to <code>2 * (<link
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Integer.MAX_VALUE">Integer.MAX_VALUE</link>
- + 1))</code> (why?) Joe's first attempt reads:</para>
+ </m:mrow>
+ </m:math>
+ </inlineequation>. Since <inlineequation>
+ <m:math display="inline">
+ <m:msup>
+ <m:mi>2</m:mi>
+
+ <m:mi>32</m:mi>
+ </m:msup>
+ </m:math>
+ </inlineequation> seems to be equal to <code>2 * (<link xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Integer.MAX_VALUE">Integer.MAX_VALUE</link> + 1))</code> (why?) Joe's first attempt reads:</para>
- <programlisting language="java" linenumbering="numbered"
- startinglinenumber="26">final long longValue = 2147483648L;
+ <programlisting language="java" linenumbering="numbered" startinglinenumber="26">final long longValue = 2147483648L;
final int reducedValue = (int) (longValue / (2 * (Integer.MAX_VALUE + 1)));
System.out.println(reducedValue);</programlisting>
- <para>Unfortunately the results are not promising. This code
- merely results in a runtime error:</para>
+ <para>Unfortunately the results are not promising. This code merely results in a runtime error:</para>
- <screen>/usr/lib/jvm/java-8-oracle/bin/java ...
+ <screen>/usr/lib/jvm/java-8-oracle/bin/java ...
Exception in thread "main" java.lang.ArithmeticException: / by zero
at qq.App.main(App.java:27)
Process finished with exit code 1</screen>
- <para>Explain the underlying problem and correct Joe's
- error.</para>
+ <para>Explain the underlying problem and correct Joe's error.</para>
- <tip>
- <para>It may be helpful thinking of a smaller example
- before. Consider hypothetic integer types
- <quote>TinyLong</quote> and <quote>TinyInt</quote> requiring
- 4 and 2 bits respectively.</para>
- </tip>
- </question>
+ <tip>
+ <para>It may be helpful thinking of a smaller example before. Consider hypothetic integer types <quote>TinyLong</quote> and <quote>TinyInt</quote> requiring 4 and 2 bits respectively.</para>
+ </tip>
+ </question>
- <answer>
- <para>As a prerequisite we represent the scaling of a
- hypothetic integer type <quote>TinyLong</quote> to a smaller
- type <quote>TinyInt</quote> of 4 and 2 bits
- respectively:</para>
+ <answer>
+ <para>As a prerequisite we represent the scaling of a hypothetic integer type <quote>TinyLong</quote> to a smaller type <quote>TinyInt</quote> of 4 and 2 bits respectively:</para>
- <informaltable border="1">
- <colgroup width="20%"/>
+ <informaltable border="1">
+ <colgroup width="20%"/>
- <colgroup width="5%"/>
+ <colgroup width="5%"/>
- <colgroup width="5%"/>
+ <colgroup width="5%"/>
- <colgroup width="5%"/>
+ <colgroup width="5%"/>
- <colgroup width="5%"/>
+ <colgroup width="5%"/>
- <colgroup width="5%"/>
+ <colgroup width="5%"/>
- <colgroup width="5%"/>
+ <colgroup width="5%"/>
- <colgroup width="5%"/>
+ <colgroup width="5%"/>
- <colgroup width="5%"/>
+ <colgroup width="5%"/>
- <colgroup width="5%"/>
+ <colgroup width="5%"/>
- <colgroup width="5%"/>
+ <colgroup width="5%"/>
- <colgroup width="5%"/>
+ <colgroup width="5%"/>
- <colgroup width="5%"/>
+ <colgroup width="5%"/>
- <colgroup width="5%"/>
+ <colgroup width="5%"/>
- <colgroup width="5%"/>
+ <colgroup width="5%"/>
- <colgroup width="5%"/>
+ <colgroup width="5%"/>
- <colgroup width="5%"/>
+ <colgroup width="5%"/>
- <tr>
- <td><quote>TinyLong</quote>, n = 4</td>
+ <tr>
+ <td><quote>TinyLong</quote>, n = 4</td>
- <td>-8</td>
+ <td>-8</td>
- <td>-7</td>
+ <td>-7</td>
- <td>-6</td>
+ <td>-6</td>
- <td>-5</td>
+ <td>-5</td>
- <td>-4</td>
+ <td>-4</td>
- <td>-3</td>
+ <td>-3</td>
- <td>-2</td>
+ <td>-2</td>
- <td>-1</td>
+ <td>-1</td>
- <td>0</td>
+ <td>0</td>
- <td>1</td>
+ <td>1</td>
- <td>2</td>
+ <td>2</td>
- <td>3</td>
+ <td>3</td>
- <td>4</td>
+ <td>4</td>
- <td>5</td>
+ <td>5</td>
- <td>6</td>
+ <td>6</td>
- <td>7</td>
- </tr>
+ <td>7</td>
+ </tr>
- <tr>
- <td><quote>TinyInt</quote>, n = 2</td>
+ <tr>
+ <td><quote>TinyInt</quote>, n = 2</td>
- <td colspan="4">-2</td>
+ <td colspan="4">-2</td>
- <td colspan="4">-1</td>
+ <td colspan="4">-1</td>
- <td colspan="4">0</td>
+ <td colspan="4">0</td>
- <td colspan="4">1</td>
- </tr>
- </informaltable>
+ <td colspan="4">1</td>
+ </tr>
+ </informaltable>
- <para>Joe's assumption for these particular values implies
- dividing <quote>TinyLong</quote> values by <inlineequation>
- <m:math display="inline">
- <m:msup>
- <m:mi>2</m:mi>
+ <para>Joe's assumption for these particular values implies dividing <quote>TinyLong</quote> values by <inlineequation>
+ <m:math display="inline">
+ <m:msup>
+ <m:mi>2</m:mi>
- <m:mi>2</m:mi>
- </m:msup>
- </m:math>
- </inlineequation> (truncating). This indeed yields the
- desired result for non-negative values. So why does Joe
- encounter a division by zero runtime exception when executing
- <code>longValue / (2 * (Integer.MAX_VALUE + 1))</code>
- ?</para>
+ <m:mi>2</m:mi>
+ </m:msup>
+ </m:math>
+ </inlineequation> (truncating). This indeed yields the desired result for non-negative values. So why does Joe encounter a division by zero runtime exception when executing <code>longValue / (2 * (Integer.MAX_VALUE + 1))</code> ?</para>
- <para>Unfortunately Joe's implementation is seriously flawed
- for even two reasons:</para>
+ <para>Unfortunately Joe's implementation is seriously flawed for even two reasons:</para>
- <orderedlist>
- <listitem>
- <para>The constant <code>Integer.MAX_VALUE</code> already
- suggests we will not be able to increase its value while
- staying as an <code>int</code>. The expression
- <code>Integer.MAX_VALUE + 1</code> will be evaluated using
- <code>int</code> rather than <code>long</code> arithmetic
- thus returning <code>Integer.MIN_VALUE</code> (negative!)
- due to an arithmetic overflow:</para>
-
- <programlisting language="java"> 01111111_11111111_11111111_11111111
+ <orderedlist>
+ <listitem>
+ <para>The constant <code>Integer.MAX_VALUE</code> already suggests we will not be able to increase its value while staying as an <code>int</code>. The expression <code>Integer.MAX_VALUE + 1</code> will be evaluated using <code>int</code> rather than <code>long</code> arithmetic thus returning <code>Integer.MIN_VALUE</code> (negative!) due to an arithmetic overflow:</para>
+
+ <programlisting language="java"> 01111111_11111111_11111111_11111111
+ 00000000_00000000_00000000_00000001
_____________________________________
10000000_00000000_00000000_00000000</programlisting>
- <para>The expression <code>2 * (Integer.MAX_VALUE +
- 1)</code> then gives rise to a second overflow
- error:</para>
+ <para>The expression <code>2 * (Integer.MAX_VALUE + 1)</code> then gives rise to a second overflow error:</para>
- <programlisting language="java"> 10000000_00000000_00000000_00000000
+ <programlisting language="java"> 10000000_00000000_00000000_00000000
+ 10000000_00000000_00000000_00000000
_____________________________________
00000000_00000000_00000000_00000000</programlisting>
- </listitem>
- </orderedlist>
-
- <para>Both errors combined (surprisingly) result in a value of
- <code>0</code> explaining the <quote>division by zero</quote>
- error message. There are two possible solutions:</para>
-
- <glosslist>
- <glossentry>
- <glossterm><code>(int) (longValue / (2L *
- (Integer.MAX_VALUE + 1L)))</code></glossterm>
-
- <glossdef>
- <para>Introducing <code>2L</code> or <code>1L</code>
- (one is sufficient) in favour of simply using 2 and 1
- turns both addition and multiplication into operations
- involving at least one long argument. Thus for both
- operations the <xref linkend="glo_Java"/> runtime will
- use <code>long</code> arithmetic returning the desired
- <quote>reducing</quote> factor of <inlineequation>
- <m:math display="inline">
- <m:msup>
- <m:mi>2</m:mi>
-
- <m:mi>32</m:mi>
- </m:msup>
- </m:math>
- </inlineequation> of type <code>long</code>.</para>
- </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm><code>(int) (longValue / 2 / (Integer.MAX_VALUE
- + 1L))</code></glossterm>
-
- <glossdef>
- <para>Same result as before.</para>
-
- <note>
- <para>This time the expression starts with
- <code>longValue / 2 ...</code> Since the variable
- <code>longValue</code> is of type <code>long</code>
- the expression <code>longValue / 2</code> will be
- evaluated by the <xref linkend="glo_Java"/> runtime
- using <code>long</code> arithmetics. The result will
- subsequently be multiplied with
- <code>Integer.MAX_VALUE + 1L</code> again using
- <code>long</code> arithmetic.</para>
- </note>
- </glossdef>
- </glossentry>
- </glosslist>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
- </section>
+ </listitem>
+ </orderedlist>
+
+ <para>Both errors combined (surprisingly) result in a value of <code>0</code> explaining the <quote>division by zero</quote> error message. There are two possible solutions:</para>
+
+ <glosslist>
+ <glossentry>
+ <glossterm><code>(int) (longValue / (2L * (Integer.MAX_VALUE + 1L)))</code></glossterm>
+
+ <glossdef>
+ <para>Introducing <code>2L</code> or <code>1L</code> (one is sufficient) in favour of simply using 2 and 1 turns both addition and multiplication into operations involving at least one long argument. Thus for both operations the <xref linkend="glo_Java"/> runtime will use <code>long</code> arithmetic returning the desired <quote>reducing</quote> factor of <inlineequation>
+ <m:math display="inline">
+ <m:msup>
+ <m:mi>2</m:mi>
+
+ <m:mi>32</m:mi>
+ </m:msup>
+ </m:math>
+ </inlineequation> of type <code>long</code>.</para>
+ </glossdef>
+ </glossentry>
+
+ <glossentry>
+ <glossterm><code>(int) (longValue / 2 / (Integer.MAX_VALUE + 1L))</code></glossterm>
+
+ <glossdef>
+ <para>Same result as before.</para>
+
+ <note>
+ <para>This time the expression starts with <code>longValue / 2 ...</code> Since the variable <code>longValue</code> is of type <code>long</code> the expression <code>longValue / 2</code> will be evaluated by the <xref linkend="glo_Java"/> runtime using <code>long</code> arithmetics. The result will subsequently be multiplied with <code>Integer.MAX_VALUE + 1L</code> again using <code>long</code> arithmetic.</para>
+ </note>
+ </glossdef>
+ </glossentry>
+ </glosslist>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
- <section xml:id="sd1SectFloatPrecisionProblem">
+ <qandaset defaultlabel="qanda" xml:id="sd1QandaFloatPrecisionProblem">
<title>Representational float and double miracles</title>
- <qandaset defaultlabel="qanda" xml:id="sd1QandaFloatPrecisionProblem">
- <qandadiv>
- <qandaentry>
- <question>
- <para>Consider and execute the following code snippet:</para>
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>Consider and execute the following code snippet:</para>
- <programlisting language="java">public static void main(String[] args) {
+ <programlisting language="java">public static void main(String[] args) {
final double a = 0.7;
final double b = 0.9;
final double x = a + 0.1;
@@ -2913,82 +2608,67 @@ _____________________________________
System.out.println(x == y);
}</programlisting>
- <para>Explain the result and supply a possible
- solution.</para>
- </question>
+ <para>Explain the result and supply a possible solution.</para>
+ </question>
- <answer>
- <para>The expression <code>x == y</code> evaluates to
- <code>false</code>. This surprising result is due to limited
- precision regarding both <code>float</code> and
- <code>double</code> IEEE representations: A given value will
- be approximated as close as possible.</para>
+ <answer>
+ <para>The expression <code>x == y</code> evaluates to <code>false</code>. This surprising result is due to limited precision regarding both <code>float</code> and <code>double</code> IEEE representations: A given value will be approximated as close as possible.</para>
- <para>Adding <code>System.out.println(x - y)</code> yields a
- value of -1.1102230246251565E-16 denoting the representational
- deviation of <code>x</code> and <code>y</code>.</para>
+ <para>Adding <code>System.out.println(x - y)</code> yields a value of -1.1102230246251565E-16 denoting the representational deviation of <code>x</code> and <code>y</code>.</para>
- <para>So we may compare <code>float</code> and
- <code>double</code> values by providing a representational
- error limit:</para>
+ <para>So we may compare <code>float</code> and <code>double</code> values by providing a representational error limit:</para>
- <programlisting language="java">final double a = 0.7;
+ <programlisting language="java">final double a = 0.7;
final double b = 0.9;
final double x = a + 0.1;
final double y = b - 0.1;
-System.out.println(<link
- xlink:href="https://docs.oracle.com/javase/8/docs/api/java/lang/Math.html#abs-double-">Math.abs</link>(x - y) < 1.E-14);</programlisting>
+System.out.println(<link xlink:href="https://docs.oracle.com/javase/8/docs/api/java/lang/Math.html#abs-double-">Math.abs</link>(x - y) < 1.E-14);</programlisting>
- <para>This implements the boolean expression <inlineequation>
- <m:math display="inline">
+ <para>This implements the boolean expression <inlineequation>
+ <m:math display="inline">
+ <m:mrow>
<m:mrow>
- <m:mrow>
- <m:mo>|</m:mo>
-
- <m:mrow>
- <m:mi>x</m:mi>
+ <m:mo>|</m:mo>
- <m:mo>-</m:mo>
+ <m:mrow>
+ <m:mi>x</m:mi>
- <m:mi>y</m:mi>
- </m:mrow>
+ <m:mo>-</m:mo>
- <m:mo>|</m:mo>
+ <m:mi>y</m:mi>
</m:mrow>
- <m:mo><</m:mo>
+ <m:mo>|</m:mo>
+ </m:mrow>
- <m:msup>
- <m:mi>10</m:mi>
+ <m:mo><</m:mo>
- <m:mrow>
- <m:mo>-</m:mo>
+ <m:msup>
+ <m:mi>10</m:mi>
- <m:mi>14</m:mi>
- </m:mrow>
- </m:msup>
- </m:mrow>
- </m:math>
- </inlineequation>.</para>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
- </section>
+ <m:mrow>
+ <m:mo>-</m:mo>
- <section xml:id="sd1SectInterestSimple">
+ <m:mi>14</m:mi>
+ </m:mrow>
+ </m:msup>
+ </m:mrow>
+ </m:math>
+ </inlineequation>.</para>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
+
+ <qandaset defaultlabel="qanda" xml:id="sd1QandaInterestSimple">
<title>Interest calculation</title>
- <qandaset defaultlabel="qanda" xml:id="sd1QandaInterestSimple">
- <qandadiv>
- <qandaentry>
- <question>
- <para>We want to calculate the compounded interest starting
- from an initial capital, a given annual interest rate and a
- duration of three years. Consider the following code
- fragment:</para>
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>We want to calculate the compounded interest starting from an initial capital, a given annual interest rate and a duration of three years. Consider the following code fragment:</para>
- <programlisting language="java"> public static void main(String[] args) {
+ <programlisting language="java"> public static void main(String[] args) {
final double initialCapital = 223.12;
final double interestRate = 1.5;
@@ -3001,43 +2681,39 @@ System.out.println(<link
System.out.println("Capital after three years:" + ...);
}</programlisting>
- <para>The expected output is:</para>
+ <para>The expected output is:</para>
- <screen>Initial capital:223.12
+ <screen>Initial capital:223.12
Annual interest rate:1.5
Capital after three years:233.31175902999993</screen>
- <tip>
- <para>In case you are unsure read about calculating the
- compounded interest.</para>
- </tip>
- </question>
+ <tip>
+ <para>In case you are unsure read about calculating the compounded interest.</para>
+ </tip>
+ </question>
- <answer>
- <para>We obtain the compounded interest by multiplying the
- initial capital by <inlineequation>
- <m:math display="inline">
- <m:mrow>
- <m:mn>1</m:mn>
+ <answer>
+ <para>We obtain the compounded interest by multiplying the initial capital by <inlineequation>
+ <m:math display="inline">
+ <m:mrow>
+ <m:mn>1</m:mn>
- <m:mo>+</m:mo>
+ <m:mo>+</m:mo>
- <m:mrow>
- <m:mi>r</m:mi>
+ <m:mrow>
+ <m:mi>r</m:mi>
- <m:mo>/</m:mo>
+ <m:mo>/</m:mo>
- <m:mn>100</m:mn>
- </m:mrow>
+ <m:mn>100</m:mn>
</m:mrow>
- </m:math>
- </inlineequation> for each year where r represents the given
- interest rate.</para>
+ </m:mrow>
+ </m:math>
+ </inlineequation> for each year where r represents the given interest rate.</para>
- <para>Since we have not yet introduced loops this
- multiplication has to be repeated three times:</para>
+ <para>Since we have not yet introduced loops this multiplication has to be repeated three times:</para>
- <programlisting language="java"> public static void main(String[] args) {
+ <programlisting language="java"> public static void main(String[] args) {
final double initialCapital = 223.12;
final double interestRate = 1.5;
@@ -3055,10 +2731,9 @@ Capital after three years:233.31175902999993</screen>
System.out.println("Capital after three years:" + capitalAtThreeYears);
}</programlisting>
- <para>We might as well use a single arithmetic expression to
- achieve the same result:</para>
+ <para>We might as well use a single arithmetic expression to achieve the same result:</para>
- <programlisting language="java"> public static void main(String[] args) {
+ <programlisting language="java"> public static void main(String[] args) {
final double initialCapital = 223.12;
final double interestRate = 1.5;
@@ -3073,225 +2748,99 @@ Capital after three years:233.31175902999993</screen>
System.out.println("Capital after three years:" + capitalAtThreeYears);
}</programlisting>
- <para>In <xref linkend="sd1InterestCalculator"/> we will
- present a more elaborate solution based on loops and class
- methods.</para>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
- </section>
+ <para>In <xref linkend="sd1InterestCalculator"/> we will present a more elaborate solution based on loops and class methods.</para>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
- <section xml:id="sd1ExpressionStrangeThings">
+ <qandaset defaultlabel="qanda" xml:id="sw1QandaByteOverflow">
<title>Strange things happen</title>
- <qandaset defaultlabel="qanda" xml:id="sw1QandaByteOverflow">
- <title>Byte integer arithmetics</title>
-
- <qandadiv>
- <qandaentry>
- <question>
- <para>Consider the following code snippet:</para>
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>Consider the following code snippet:</para>
- <programlisting language="java">byte a = 127;
+ <programlisting language="java">byte a = 127;
System.out.println("value=" + a);
a++;
System.out.println("New value=" + a);
</programlisting>
- <para>This will produce the following output:</para>
+ <para>This will produce the following output:</para>
- <screen>value=127
+ <screen>value=127
New value=-128</screen>
- <para>Explain this strange behaviour.</para>
+ <para>Explain this strange behaviour.</para>
- <para>Moreover you'll find the following code snippet yields a
- compile time error:</para>
+ <para>Moreover you'll find the following code snippet yields a compile time error:</para>
- <programlisting language="java">byte a = 127;
+ <programlisting language="java">byte a = 127;
System.out.println("value=" + a);
a = a + 1; // Error: Type mismatch: cannot convert from int to byte
System.out.println("New value=" + a);</programlisting>
- <para>Explain this error's cause.</para>
+ <para>Explain this error's cause.</para>
- <tip>
- <para>You may want to read the <link
- xlink:href="https://proquest.safaribooksonline.com/9780992133047/toc1_html_4">overview
- section</link> on statements.</para>
- </tip>
- </question>
+ <tip>
+ <para>You may want to read the <link xlink:href="https://proquest.safaribooksonline.com/9780992133047/toc1_html_4">overview section</link> on statements.</para>
+ </tip>
+ </question>
- <answer>
- <para>A byte variable ranges from -128 to +127. Thus
- incrementing 127 by 1 yields -128 and thus an overflow
- error.</para>
+ <answer>
+ <para>A byte variable ranges from -128 to +127. Thus incrementing 127 by 1 yields -128 and thus an overflow error.</para>
- <para>Since <xref linkend="glo_Java"/> uses <link
- xlink:href="https://en.wikipedia.org/wiki/Two's_complement#firstHeading">Two's
- complement</link> representation we have:</para>
+ <para>Since <xref linkend="glo_Java"/> uses <link xlink:href="https://en.wikipedia.org/wiki/Two's_complement#firstHeading">Two's complement</link> representation we have:</para>
- <informaltable border="1">
- <tr>
- <td><code> 01111111</code></td>
+ <informaltable border="1">
+ <tr>
+ <td><code> 01111111</code></td>
- <td><code> 127</code></td>
- </tr>
+ <td><code> 127</code></td>
+ </tr>
- <tr>
- <td><code>+00000001</code></td>
+ <tr>
+ <td><code>+00000001</code></td>
- <td><code> +1</code></td>
- </tr>
+ <td><code> +1</code></td>
+ </tr>
- <tr>
- <td><code>=10000000</code></td>
+ <tr>
+ <td><code>=10000000</code></td>
- <td><code>=-128</code></td>
- </tr>
- </informaltable>
+ <td><code>=-128</code></td>
+ </tr>
+ </informaltable>
- <para>On machine level the above calculation is just an
- ordinary addition.</para>
+ <para>On machine level the above calculation is just an ordinary addition.</para>
- <para>Conclusion: Watch out when doing (integer)
- arithmetic!</para>
+ <para>Conclusion: Watch out when doing (integer) arithmetic!</para>
- <para>The compile time error is due to the definition of the
- <quote>+</quote> operator in Java always returning an
- <code>int</code> rather than a byte. Consider:</para>
+ <para>The compile time error is due to the definition of the <quote>+</quote> operator in Java always returning an <code>int</code> rather than a byte. Consider:</para>
- <programlisting language="java"> byte a = 120, b = 10;
+ <programlisting language="java"> byte a = 120, b = 10;
System.out.println(a + b);</programlisting>
- <para>This yields the expected output of 130 and corresponds
- to an <code>int</code> value.</para>
+ <para>This yields the expected output of 130 and corresponds to an <code>int</code> value.</para>
- <para>If the expression <code>a + b</code> was of data type
- <code>byte</code> an arithmetic overflow as in the subsequent
- code example would occur:</para>
+ <para>If the expression <code>a + b</code> was of data type <code>byte</code> an arithmetic overflow as in the subsequent code example would occur:</para>
- <programlisting language="java"> byte a = 120, b = 10;
+ <programlisting language="java"> byte a = 120, b = 10;
byte sum = (byte) (a + b);
System.out.println(sum);</programlisting>
- <para>The explicit type conversion (a so called type cast or
- cast for short) forces the 4-byte integer into a one-byte
- variable <code>sum</code> thereby loosing the original value
- and returning -126 instead.</para>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
- </section>
+ <para>The explicit type conversion (a so called type cast or cast for short) forces the 4-byte integer into a one-byte variable <code>sum</code> thereby loosing the original value and returning -126 instead.</para>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
<section xml:id="sw1SectAssignArithmetics">
<title>Assignments and simple arithmetics</title>
-
- <qandaset defaultlabel="qanda" xml:id="sw1QandaGuessingResults">
- <title>Guessing results</title>
-
- <qandadiv>
- <qandaentry>
- <question>
- <para>Consider the following code segment:</para>
-
- <programlisting language="java"> int a = 3;
- a++; //Incrementing a by 1 --> a==4
-
- int b = a; // TODO
-
- b--; // TODO
- --b; // TODO
-
- int c = b; // TODO
-
- b = ++a; // TODO
- int e = a++; // TODO
-
- a *= b; // TODO
-
- System.out.println("a=" + a);
- System.out.println("b=" + b);
- System.out.println("c=" + c);
- System.out.println("e=" + e);</programlisting>
-
- <para>We want to guess the expected result. Copy/paste the
- above code into a main() method body within your IDE of choice
- (probably Eclipse). Though it is tempting to just execute this
- code ant watch the results <emphasis role="bold">please
- refrain from doing so!</emphasis></para>
-
- <para>Instead start a <quote>dry run</quote> complete the
- above comments to predict the expected outcome:</para>
-
- <para><computeroutput>a=...</computeroutput></para>
-
- <para><computeroutput>b=...</computeroutput></para>
-
- <para><computeroutput>c=...</computeroutput></para>
-
- <para><computeroutput>e=...</computeroutput></para>
-
- <para>After finishing your guesses execute your code and start
- wailing about your success rate.</para>
-
- <tip>
- <para>Both <code>x++</code> (postfix notation) and
- <code>++x</code> (infix notation) are expressions themselves
- which might even be rewritten as <code>(x++)</code> and
- <code>(++x)</code> for the sake of clarity. The difference
- is not about operator precedence rules but simply about the
- values of these expressions when being assigned to other
- variables.</para>
- </tip>
- </question>
-
- <answer>
- <para>As inferred by the hint the biggest problem is about
- understanding postfix and infix notation of the operators
- <code>++</code> and <code>--</code>. A corresponding
- expression evaluates to:</para>
-
- <itemizedlist>
- <listitem>
- <para><code>a = x++</code> yields a ==x</para>
- </listitem>
-
- <listitem>
- <para><code>a = ++x</code> yields a ==(x + 1)</para>
- </listitem>
- </itemizedlist>
-
- <para>The rest is just obeying the <quote>due
- diligence</quote> rule set:</para>
-
- <programlisting language="java"> int a = 3;
- a++; //Incrementing a by 1 --> a==4
-
- int b = a; // Assigning value of a --> b==4
-
- b--; // Decrementing b by 1 --> b==3
- --b; // Decrementing b by 1 --> b==2
-
- int c = b; // c == 2;
-
- b = ++a; // Incrementing a by 1 -->a==5, then assigning to b --> b == 5
- int e = a++; // Assigning a to e --> e==5, then incrementing a --> a==6
-
- a *= b; // Multiplying a with b and assigning the result to a --> a==30
-
- System.out.println("a=" + a);
- System.out.println("b=" + b);
- System.out.println("c=" + c);
- System.out.println("e=" + e);</programlisting>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
</section>
</section>
@@ -3313,8 +2862,7 @@ System.out.println("New value=" + a);</programlisting>
}</programlisting>
- <para>Complete the above snippet to produce the following
- output:</para>
+ <para>Complete the above snippet to produce the following output:</para>
<screen>3 Games having 22 players each results in 66 players altogether.</screen>
</question>
@@ -3345,17 +2893,10 @@ System.out.println("New value=" + a);</programlisting>
System.out.println("Some 'special' words.");
}</programlisting>
- <para>The corresponding output will be <computeroutput>Some
- 'special' words.</computeroutput>. Change the above code to
- replace the single quotes by double quotes producing the output
- <computeroutput>Some "special" words.</computeroutput>
- instead.</para>
+ <para>The corresponding output will be <computeroutput>Some 'special' words.</computeroutput>. Change the above code to replace the single quotes by double quotes producing the output <computeroutput>Some "special" words.</computeroutput> instead.</para>
<tip>
- <para>Hunt for <quote>java escape double quote</quote> and
- read about <link
- xlink:href="https://proquest.safaribooksonline.com/book/programming/java/9780992133047/chapter-2-language-fundamentals/toc6_html_2#readertoolbar2">character
- literals</link>.</para>
+ <para>Hunt for <quote>java escape double quote</quote> and read about <link xlink:href="https://proquest.safaribooksonline.com/book/programming/java/9780992133047/chapter-2-language-fundamentals/toc6_html_2#readertoolbar2">character literals</link>.</para>
</tip>
</question>
@@ -3367,8 +2908,7 @@ System.out.println("New value=" + a);</programlisting>
<glossterm>Perfectly obvious</glossterm>
<glossdef>
- <para>Inside a string literal the string terminating
- character (") may be escaped using backslashes:</para>
+ <para>Inside a string literal the string terminating character (") may be escaped using backslashes:</para>
<programlisting language="java">System.out.println("Some \"special\" words.");</programlisting>
</glossdef>
@@ -3378,8 +2918,7 @@ System.out.println("New value=" + a);</programlisting>
<glossterm>Even more clumsy</glossterm>
<glossdef>
- <para>Double quotes may be also represented by their char
- (not string!) literal:</para>
+ <para>Double quotes may be also represented by their char (not string!) literal:</para>
<programlisting language="java">System.out.println("Some " + '"' + "special" + '"' + " words.");</programlisting>
</glossdef>
@@ -3396,23 +2935,19 @@ System.out.println("New value=" + a);</programlisting>
<qandadiv>
<qandaentry>
<question>
- <para xml:id="sw1QandaStringCodingBatExtra">Solve the following
- external exercises:</para>
+ <para xml:id="sw1QandaStringCodingBatExtra">Solve the following external exercises:</para>
<itemizedlist>
<listitem>
- <para
- xlink:href="http://codingbat.com/prob/p171896">helloName</para>
+ <para xlink:href="http://codingbat.com/prob/p171896">helloName</para>
</listitem>
<listitem>
- <para
- xlink:href="http://codingbat.com/prob/p161056">makeAbba</para>
+ <para xlink:href="http://codingbat.com/prob/p161056">makeAbba</para>
</listitem>
<listitem>
- <para
- xlink:href="http://codingbat.com/prob/p147483">makeTags</para>
+ <para xlink:href="http://codingbat.com/prob/p147483">makeTags</para>
</listitem>
</itemizedlist>
</question>
@@ -3425,14 +2960,12 @@ System.out.println("New value=" + a);</programlisting>
<title>Using <code>final</code></title>
<qandaset defaultlabel="qanda" xml:id="sw1QandaCircleAreaFinal">
- <title>Calculating the area of a circle avoiding accidental
- redefinition</title>
+ <title>Calculating the area of a circle avoiding accidental redefinition</title>
<qandadiv>
<qandaentry>
<question>
- <para>In Exercise <xref linkend="sd1SectCircleArea"/> you
- calculated a given circle's area:</para>
+ <para>In Exercise <xref linkend="sw1QandaCircleArea"/> you calculated a given circle's area:</para>
<programlisting language="java"> public static void main(String[] args) {
@@ -3444,9 +2977,7 @@ System.out.println("New value=" + a);</programlisting>
System.out.println(area);
}</programlisting>
- <para>Though there is nothing wrong with this approach it
- actually is error prone: A careless programmer may accidentally
- redefine the value of <code>pi</code>:</para>
+ <para>Though there is nothing wrong with this approach it actually is error prone: A careless programmer may accidentally redefine the value of <code>pi</code>:</para>
<programlisting language="java"> public static void main(String[] args) {
@@ -3466,20 +2997,15 @@ System.out.println("New value=" + a);</programlisting>
System.out.println(area);
}</programlisting>
- <para>Modify the original code to avoid this type of
- error.</para>
+ <para>Modify the original code to avoid this type of error.</para>
<tip>
- <para>You may want to read the <quote
- xlink:href="https://proquest.safaribooksonline.com/9780992133047/toc5_html_2">Constants</quote>
- section of <xref linkend="bib_Kurniawan2015"/>.</para>
+ <para>You may want to read the <quote xlink:href="https://proquest.safaribooksonline.com/9780992133047/toc5_html_2">Constants</quote> section of <xref linkend="bib_Kurniawan2015"/>.</para>
</tip>
</question>
<answer>
- <para>The solution is straightforward. We add the
- <code>final</code> modifier to the definition of our variable
- <code>pi</code>:</para>
+ <para>The solution is straightforward. We add the <code>final</code> modifier to the definition of our variable <code>pi</code>:</para>
<programlisting language="java" linenumbering="numbered">public static void main(String[] args) {
@@ -3499,20 +3025,13 @@ System.out.println("New value=" + a);</programlisting>
System.out.println(area);
}</programlisting>
- <para>Now our flawed assignment at line 9 will be flagged as a
- compile time error:</para>
+ <para>Now our flawed assignment at line 9 will be flagged as a compile time error:</para>
- <para><computeroutput>The final local variable pi cannot be
- assigned. It must be blank and not using a compound
- assignment</computeroutput></para>
+ <para><computeroutput>The final local variable pi cannot be assigned. It must be blank and not using a compound assignment</computeroutput></para>
- <para>Note the second <code>final</code> modification in the
- definition of our variable <code>area</code> to avoid erroneous
- redefinitions as well.</para>
+ <para>Note the second <code>final</code> modification in the definition of our variable <code>area</code> to avoid erroneous redefinitions as well.</para>
- <para>As a rule of thumb: Whenever you intend a variable not to
- change after an initial assignment use <code>final</code>
- declaring it to remain constant.</para>
+ <para>As a rule of thumb: Whenever you intend a variable not to change after an initial assignment use <code>final</code> declaring it to remain constant.</para>
</answer>
</qandaentry>
</qandadiv>
@@ -3538,14 +3057,11 @@ System.out.println("New value=" + a);</programlisting>
}</programlisting>
- <para>This will run smoothly producing the expected
- output:</para>
+ <para>This will run smoothly producing the expected output:</para>
<screen>20 + 3 + 9 = 32</screen>
- <para>We now prettify our variable definitions by introducing
- right aligning numbers thereby padding leading positions with
- zeros:</para>
+ <para>We now prettify our variable definitions by introducing right aligning numbers thereby padding leading positions with zeros:</para>
<programlisting language="java"> public static void main(String[] args) {
@@ -3556,24 +3072,17 @@ System.out.println("New value=" + a);</programlisting>
System.out.println(a + " + " + b + " + " + c + " = " + (a + b + c));
}</programlisting>
- <para>The above code does not compile due to the compiler error
- when defining variable <code>c</code>.</para>
+ <para>The above code does not compile due to the compiler error when defining variable <code>c</code>.</para>
- <para>Explain the underlying cause of this error message. Why is
- <code>b = 03</code> just fine in contrast to <code>c = 09</code>
- ?</para>
+ <para>Explain the underlying cause of this error message. Why is <code>b = 03</code> just fine in contrast to <code>c = 09</code> ?</para>
<tip>
- <para>Re-read the section on integer literal
- representations.</para>
+ <para>Re-read the section on integer literal representations.</para>
</tip>
</question>
<answer>
- <para>Integer literals starting with <quote>0</quote> are being
- interpreted as octal representation. Since the octal system's
- set of digits is {0,1,2,3,4,5,6,7} the value <quote>09</quote>
- is simply not valid.</para>
+ <para>Integer literals starting with <quote>0</quote> are being interpreted as octal representation. Since the octal system's set of digits is {0,1,2,3,4,5,6,7} the value <quote>09</quote> is simply not valid.</para>
</answer>
</qandaentry>
</qandadiv>
@@ -3593,19 +3102,13 @@ System.out.println("New value=" + a);</programlisting>
System.out.println("Value = " + a);
}</programlisting>
- <para>On execution we receive the output <code>Value =
- 33</code>. Explain this result</para>
+ <para>On execution we receive the output <code>Value = 33</code>. Explain this result</para>
</question>
<answer>
- <para>This problem is related to the previous exercise: The
- integer literal 041 defines octal representation. Changing from
- octal to decimal representation takes us to 4 * 8 + 1 =
- 33.</para>
-
- <para>There are 11 types of people: Those, who know can read
- binary codes, those who know what binary is and those who don't
- have a clue what binary is.</para>
+ <para>This problem is related to the previous exercise: The integer literal 041 defines octal representation. Changing from octal to decimal representation takes us to 4 * 8 + 1 = 33.</para>
+
+ <para>There are 11 types of people: Those, who know can read binary codes, those who know what binary is and those who don't have a clue what binary is.</para>
</answer>
</qandaentry>
</qandadiv>
diff --git a/ws/Docbook/CustomLayer/webhelp/positioning.css.patch b/ws/Docbook/CustomLayer/webhelp/positioning.css.patch
index ccdd56d2125960e13ff81dd8482f7510fbdd74e1..aa0acdade1becbc4be66743fa6becfa3453b8541 100644
--- a/ws/Docbook/CustomLayer/webhelp/positioning.css.patch
+++ b/ws/Docbook/CustomLayer/webhelp/positioning.css.patch
@@ -1,5 +1,5 @@
---- positioning.css.orig 2017-07-26 08:31:17.880119353 +0200
-+++ positioning.css 2017-07-25 17:39:11.215083986 +0200
+--- positioning.css.orig 2017-07-26 16:38:34.708386065 +0200
++++ positioning.css 2017-07-26 16:35:36.955120822 +0200
@@ -1,3 +1,8 @@
+/*
+ * patched by: /usr/share/hdm-docbook-xsl/CustomLayer/webhelp/positioning.css.patch
@@ -9,26 +9,33 @@
tr th .added { color: #E6E6FA; }
tr th .changed {color: #99ff99; }
div.added tr, div.added { background-color: #E6E6FA; }
-@@ -328,9 +333,16 @@
+@@ -328,11 +333,23 @@
div#toolbar-left img {vertical-align: text-top;}
div.note *, div.caution *, div.important *, div.tip *, div.warning * {
- background: inherit !important;
+ width: fit-content;
-+ border-radius: 10px;
-+ padding: 5px;
-+ background: var(--admonitionBackgroundColor) !important;
color: inherit !important;
- border: inherit !important;
++ /* border: inherit !important; */
++}
++
++div.note, div.caution, div.important, div.tip, div.warning {
++ width: fit-content;
++ background: var(--admonitionBackgroundColor) !important;
++ border-radius: 10px;
++ padding: 5px;
+ border-style: solid;
+ border-color: #AAAAAA;
+ border-width: 1px;
-+
-+ /* border: inherit !important; */
}
++
++
#content table thead, #content table th{
-@@ -375,3 +387,109 @@
+ background: gray;
+ color: white;
+@@ -375,3 +392,109 @@
}
diff --git a/ws/Docbook/Extensions/Tdata/Components/exampleSlides.xml b/ws/Docbook/Extensions/Tdata/Components/exampleSlides.xml
index a3a9fc0c7ed7f9d3b72048b40f3227151d3bd924..4ffb25428477a249a0c015f9a033743e2d94c15b 100644
--- a/ws/Docbook/Extensions/Tdata/Components/exampleSlides.xml
+++ b/ws/Docbook/Extensions/Tdata/Components/exampleSlides.xml
@@ -1,14 +1,5 @@
<?xml version="1.0" encoding="UTF-8"?>
-<chapter version="5.1" xml:id="mixLectureSlides"
- xmlns="http://docbook.org/ns/docbook"
- xmlns:xlink="http://www.w3.org/1999/xlink"
- xmlns:xila="http://www.w3.org/2001/XInclude/local-attributes"
- xmlns:xi="http://www.w3.org/2001/XInclude"
- xmlns:trans="http://docbook.org/ns/transclusion"
- xmlns:svg="http://www.w3.org/2000/svg"
- xmlns:m="http://www.w3.org/1998/Math/MathML"
- xmlns:html="http://www.w3.org/1999/xhtml"
- xmlns:db="http://docbook.org/ns/docbook">
+<chapter version="5.1" xml:id="mixLectureSlides" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xila="http://www.w3.org/2001/XInclude/local-attributes" xmlns:xi="http://www.w3.org/2001/XInclude" xmlns:trans="http://docbook.org/ns/transclusion" xmlns:svg="http://www.w3.org/2000/svg" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:html="http://www.w3.org/1999/xhtml" xmlns:db="http://docbook.org/ns/docbook">
<title>Mixing lecture notes and slides</title>
<section annotations="slide" xml:id="classintro">
@@ -54,18 +45,15 @@
<figure xml:id="fig_ClassExample">
<title>General class syntax</title>
- <programlisting language="java">public class TestImg { <co
- linkends="javaExample-1" xml:id="javaExample-1-co"/>
+ <programlisting language="java">public class TestImg { <co linkends="javaExample-1" xml:id="javaExample-1-co"/>
/**
- * @throws JDOMException Corrupt content, failing to parse. <co
- linkends="javaExample-2" xml:id="javaExample-2-co"/>
+ * @throws JDOMException Corrupt content, failing to parse. <co linkends="javaExample-2" xml:id="javaExample-2-co"/>
* @throws IOException File access problem.
*/
@SuppressWarnings("static-method")
@Test
- public void testCsv() throws JDOMException, IOException { <co
- linkends="javaExample-3" xml:id="javaExample-3-co"/></programlisting>
+ public void testCsv() throws JDOMException, IOException { <co linkends="javaExample-3" xml:id="javaExample-3-co"/></programlisting>
<calloutlist>
<callout arearefs="javaExample-1-co" xml:id="javaExample-1">
@@ -81,13 +69,16 @@
</callout>
</calloutlist>
</figure>
+
+ <tip>
+ <para>You may require a <code>return</code> statement as well.</para>
+ </tip>
</section>
<section xml:id="exampleScreen">
<title>Screen</title>
- <para>The output of <command>ls</command> <option>-al</option>
- reads:</para>
+ <para>The output of <command>ls</command> <option>-al</option> reads:</para>
<screen>goik@hopc Downloads> ls -al
total 548
@@ -108,18 +99,15 @@ drwxr-xr-x 100 goik fb1prof 12288 Jul 13 07:43 ..
<mediaobject>
<imageobjectco>
<areaspec otherunits="imagemap" units="other">
- <area coords="83,16,340,187" linkends="calloutSeat"
- xml:id="seat">
+ <area coords="83,16,340,187" linkends="calloutSeat" xml:id="seat">
<alt>Seat</alt>
</area>
- <area coords="511,345,550,380" linkends="calloutValve"
- xml:id="valveFront">
+ <area coords="511,345,550,380" linkends="calloutValve" xml:id="valveFront">
<alt>Valve</alt>
</area>
- <area coords="112,335,151,370" linkends="calloutValve"
- xml:id="valveBack">
+ <area coords="112,335,151,370" linkends="calloutValve" xml:id="valveBack">
<alt>Valve</alt>
</area>
</areaspec>
@@ -354,10 +342,7 @@ drwxr-xr-x 100 goik fb1prof 12288 Jul 13 07:43 ..
<m:mi>2</m:mi>
</m:mrow>
</m:math>
- </inlineequation> or <code
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Long.MAX_VALUE"><varname
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Long.MAX_VALUE">Long.MAX_VALUE</varname></code>
- - 1</td>
+ </inlineequation> or <code xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Long.MAX_VALUE"><varname xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Long.MAX_VALUE">Long.MAX_VALUE</varname></code> - 1</td>
<td align="right">2147483647</td>
@@ -375,8 +360,7 @@ drwxr-xr-x 100 goik fb1prof 12288 Jul 13 07:43 ..
<m:mi>1</m:mi>
</m:mrow>
</m:math>
- </inlineequation> or <varname
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Integer.MAX_VALUE">Integer.MAX_VALUE</varname></td>
+ </inlineequation> or <varname xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Integer.MAX_VALUE">Integer.MAX_VALUE</varname></td>
</tr>
<tr>
@@ -396,8 +380,7 @@ drwxr-xr-x 100 goik fb1prof 12288 Jul 13 07:43 ..
<m:mi>1</m:mi>
</m:mrow>
</m:math>
- </inlineequation> or <varname
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Long.MAX_VALUE">Long.MAX_VALUE</varname></td>
+ </inlineequation> or <varname xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Long.MAX_VALUE">Long.MAX_VALUE</varname></td>
<td align="right">2147483647</td>
@@ -415,8 +398,7 @@ drwxr-xr-x 100 goik fb1prof 12288 Jul 13 07:43 ..
<m:mi>1</m:mi>
</m:mrow>
</m:math>
- </inlineequation> or <varname
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Integer.MAX_VALUE">Integer.MAX_VALUE</varname></td>
+ </inlineequation> or <varname xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Integer.MAX_VALUE">Integer.MAX_VALUE</varname></td>
</tr>
</informaltable>
</tip>
@@ -572,10 +554,7 @@ drwxr-xr-x 100 goik fb1prof 12288 Jul 13 07:43 ..
<m:mi>2</m:mi>
</m:mrow>
</m:math>
- </inlineequation> or <code
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Long.MAX_VALUE"><varname
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Long.MAX_VALUE">Long.MAX_VALUE</varname></code>
- - 1</td>
+ </inlineequation> or <code xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Long.MAX_VALUE"><varname xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Long.MAX_VALUE">Long.MAX_VALUE</varname></code> - 1</td>
<td align="right">2147483647</td>
@@ -593,8 +572,7 @@ drwxr-xr-x 100 goik fb1prof 12288 Jul 13 07:43 ..
<m:mi>1</m:mi>
</m:mrow>
</m:math>
- </inlineequation> or <varname
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Integer.MAX_VALUE">Integer.MAX_VALUE</varname></td>
+ </inlineequation> or <varname xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Integer.MAX_VALUE">Integer.MAX_VALUE</varname></td>
</tr>
<tr>
@@ -614,8 +592,7 @@ drwxr-xr-x 100 goik fb1prof 12288 Jul 13 07:43 ..
<m:mi>1</m:mi>
</m:mrow>
</m:math>
- </inlineequation> or <varname
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Long.MAX_VALUE">Long.MAX_VALUE</varname></td>
+ </inlineequation> or <varname xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Long.MAX_VALUE">Long.MAX_VALUE</varname></td>
<td align="right">2147483647</td>
@@ -633,8 +610,7 @@ drwxr-xr-x 100 goik fb1prof 12288 Jul 13 07:43 ..
<m:mi>1</m:mi>
</m:mrow>
</m:math>
- </inlineequation> or <varname
- xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Integer.MAX_VALUE">Integer.MAX_VALUE</varname></td>
+ </inlineequation> or <varname xlink:href="https://docs.oracle.com/javase/8/docs/api/constant-values.html#java.lang.Integer.MAX_VALUE">Integer.MAX_VALUE</varname></td>
</tr>
</informaltable>
</figure>