From 1f7c31c3921498ec4d1cff6623a8dbd332f43c0b Mon Sep 17 00:00:00 2001
From: Martin Goik <goik@hdm-stuttgart.de>
Date: Wed, 30 Oct 2019 11:35:21 +0100
Subject: [PATCH] sub chapters else and elese-if
---
Doc/Sd1/statements.xml | 1567 ++++++++++++++++++++--------------------
1 file changed, 792 insertions(+), 775 deletions(-)
diff --git a/Doc/Sd1/statements.xml b/Doc/Sd1/statements.xml
index b3b079c2b..b6c433875 100644
--- a/Doc/Sd1/statements.xml
+++ b/Doc/Sd1/statements.xml
@@ -221,26 +221,29 @@ System.out.println("Done!");</programlisting></td>
(block | statement)</programlisting>
</figure>
- <figure xml:id="sd1_fig_ifElse">
- <title><code language="java">if</code> ... <code
- language="java">else</code> block execution selection</title>
+ <section xml:id="sd1_sect_else">
+ <title>if-then-<code>else</code></title>
- <informaltable border="1">
- <colgroup width="37%"/>
+ <figure xml:id="sd1_fig_ifElse">
+ <title><code language="java">if</code> ... <code
+ language="java">else</code> block execution selection</title>
- <colgroup width="63%"/>
+ <informaltable border="1">
+ <colgroup width="37%"/>
- <tr>
- <td valign="top"><programlisting language="java">double saving = 320.00;
+ <colgroup width="63%"/>
+
+ <tr>
+ <td valign="top"><programlisting language="java">double saving = 320.00;
if (1000 <= saving <co linkends="sd1_fig_ifElse-1"
- xml:id="sd1_fig_ifElse-1-co"/>) { <co
- linkends="sd1_fig_ifElse-2" xml:id="sd1_fig_ifElse-2-co"/>
+ xml:id="sd1_fig_ifElse-1-co"/>) { <co
+ linkends="sd1_fig_ifElse-2" xml:id="sd1_fig_ifElse-2-co"/>
// Rich customer, 1,2% interest rate
System.out.println(
"Interest:" + 1.2 * saving / 100);
} <co linkends="sd1_fig_ifElse-3" xml:id="sd1_fig_ifElse-3-co"/> else { <co
- linkends="sd1_fig_ifElse-4" xml:id="sd1_fig_ifElse-4-co"/>
+ linkends="sd1_fig_ifElse-4" xml:id="sd1_fig_ifElse-4-co"/>
// Joe customer, 0.8% standard interest rate
System.out.println(
"Interest:" + 0.8 * saving / 100);
@@ -248,134 +251,137 @@ if (1000 <= saving <co linkends="sd1_fig_ifElse-1"
System.out.println("Done!");</programlisting><screen>Interest:2.56
Done!</screen></td>
- <td valign="top"><mediaobject>
- <imageobject>
- <imagedata fileref="Ref/Statements/ifElse.svg"/>
- </imageobject>
- </mediaobject></td>
- </tr>
- </informaltable>
+ <td valign="top"><mediaobject>
+ <imageobject>
+ <imagedata fileref="Ref/Statements/ifElse.svg"/>
+ </imageobject>
+ </mediaobject></td>
+ </tr>
+ </informaltable>
- <calloutlist role="slideExclude">
- <callout arearefs="sd1_fig_ifElse-1-co" xml:id="sd1_fig_ifElse-1">
- <para>Decision on boolean expression.</para>
- </callout>
-
- <callout arearefs="sd1_fig_ifElse-2-co" xml:id="sd1_fig_ifElse-2">
- <para>Conditional execution of on block or single statement.</para>
- </callout>
-
- <callout arearefs="sd1_fig_ifElse-3-co" xml:id="sd1_fig_ifElse-3">
- <para>Required branch being executed in case of boolean expression
- being true.</para>
- </callout>
-
- <callout arearefs="sd1_fig_ifElse-4-co" xml:id="sd1_fig_ifElse-4">
- <para>Optional branch corresponding to boolean expression being
- false.</para>
- </callout>
- </calloutlist>
- </figure>
+ <calloutlist role="slideExclude">
+ <callout arearefs="sd1_fig_ifElse-1-co" xml:id="sd1_fig_ifElse-1">
+ <para>Decision on boolean expression.</para>
+ </callout>
- <figure xml:id="sd1_fig_ifElseSyntax">
- <title><code language="java">if ... else</code> execution syntax</title>
+ <callout arearefs="sd1_fig_ifElse-2-co" xml:id="sd1_fig_ifElse-2">
+ <para>Conditional execution of on block or single
+ statement.</para>
+ </callout>
- <programlisting language="java">if (booleanExpression)
+ <callout arearefs="sd1_fig_ifElse-3-co" xml:id="sd1_fig_ifElse-3">
+ <para>Required branch being executed in case of boolean expression
+ being true.</para>
+ </callout>
+
+ <callout arearefs="sd1_fig_ifElse-4-co" xml:id="sd1_fig_ifElse-4">
+ <para>Optional branch corresponding to boolean expression being
+ false.</para>
+ </callout>
+ </calloutlist>
+ </figure>
+
+ <figure xml:id="sd1_fig_ifElseSyntax">
+ <title><code language="java">if ... else</code> execution
+ syntax</title>
+
+ <programlisting language="java">if (booleanExpression)
(block | statement)
[else
(block | statement) ] <co linkends="sd1_fig_ifElseSyntax-1"
- xml:id="sd1_fig_ifElseSyntax-1-co"/></programlisting>
-
- <calloutlist role="slideExclude">
- <callout arearefs="sd1_fig_ifElseSyntax-1-co"
- xml:id="sd1_fig_ifElseSyntax-1">
- <para>The <quote>[...]</quote> pair of braces denotes an optional
- clause that may or may not be present.</para>
-
- <para>Thus only the first part <quote><code language="java">if
- (booleanExpression) (block | statement)</code></quote> is
- mandatory.</para>
- </callout>
- </calloutlist>
- </figure>
+ xml:id="sd1_fig_ifElseSyntax-1-co"/></programlisting>
+
+ <calloutlist role="slideExclude">
+ <callout arearefs="sd1_fig_ifElseSyntax-1-co"
+ xml:id="sd1_fig_ifElseSyntax-1">
+ <para>The <quote>[...]</quote> pair of braces denotes an optional
+ clause that may or may not be present.</para>
+
+ <para>Thus only the first part <quote><code language="java">if
+ (booleanExpression) (block | statement)</code></quote> is
+ mandatory.</para>
+ </callout>
+ </calloutlist>
+ </figure>
- <figure xml:id="sd1_fig_bestPracticeCompareEquals">
- <title>Best practices comparing for equality</title>
+ <figure xml:id="sd1_fig_bestPracticeCompareEquals">
+ <title>Best practices comparing for equality</title>
- <para>Always use</para>
+ <para>Always use</para>
- <programlisting language="java">if (4 == variable) ...</programlisting>
+ <programlisting language="java">if (4 == variable) ...</programlisting>
- <para>in favour of:</para>
+ <para>in favour of:</para>
- <programlisting language="java">if (variable == 4) ...</programlisting>
+ <programlisting language="java">if (variable == 4) ...</programlisting>
- <para>See <link
- xlink:href="sd1_sect_statements_if.html#sd1_note_useLiteralEqualsVariable">detailed
- explanation</link>.</para>
- </figure>
+ <para>See <link
+ xlink:href="sd1_sect_statements_if.html#sd1_note_useLiteralEqualsVariable">detailed
+ explanation</link>.</para>
+ </figure>
- <qandaset defaultlabel="qanda" xml:id="sd1_qanda_betterSimpleMath">
- <title>Providing better display</title>
+ <qandaset defaultlabel="qanda" xml:id="sd1_qanda_betterSimpleMath">
+ <title>Providing better display</title>
- <qandadiv>
- <qandaentry>
- <question>
- <para>We reconsider <xref linkend="sd1_qanda_simpleMath"/>:</para>
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>We reconsider <xref
+ linkend="sd1_qanda_simpleMath"/>:</para>
- <informaltable border="0">
- <tr>
- <th>Source code</th>
+ <informaltable border="0">
+ <tr>
+ <th>Source code</th>
- <th>Output</th>
- </tr>
+ <th>Output</th>
+ </tr>
- <tr>
- <td valign="top"><programlisting language="java">int a = -4,
+ <tr>
+ <td valign="top"><programlisting language="java">int a = -4,
b = 100;
System.out.println(a + "+" + b+ "=" + (a + b));</programlisting></td>
- <td valign="top"><screen>-4+100=96</screen></td>
- </tr>
- </informaltable>
+ <td valign="top"><screen>-4+100=96</screen></td>
+ </tr>
+ </informaltable>
- <para>Unfortunately changing the two variables' values
- yields:</para>
+ <para>Unfortunately changing the two variables' values
+ yields:</para>
- <informaltable border="0">
- <tr>
- <th>Source code</th>
+ <informaltable border="0">
+ <tr>
+ <th>Source code</th>
- <th>Output</th>
- </tr>
+ <th>Output</th>
+ </tr>
- <tr>
- <td valign="top"><programlisting language="java">int a = 100,
+ <tr>
+ <td valign="top"><programlisting language="java">int a = 100,
b = -4;
System.out.println(a + "+" + b + "=" + (a + b));</programlisting></td>
- <td valign="top"><screen>100+-4=96</screen></td>
- </tr>
- </informaltable>
+ <td valign="top"><screen>100+-4=96</screen></td>
+ </tr>
+ </informaltable>
- <para>This result looks awkward. Modify the code to see
- <code>100-4=96</code> in such cases.</para>
- </question>
+ <para>This result looks awkward. Modify the code to see
+ <code>100-4=96</code> in such cases.</para>
+ </question>
- <answer>
- <para>The following simple solution does not work:</para>
+ <answer>
+ <para>The following simple solution does not work:</para>
- <informaltable border="0">
- <tr>
- <th>Source code</th>
+ <informaltable border="0">
+ <tr>
+ <th>Source code</th>
- <th>Output</th>
- </tr>
+ <th>Output</th>
+ </tr>
- <tr>
- <td valign="top"><programlisting language="java">int a = 100,
+ <tr>
+ <td valign="top"><programlisting language="java">int a = 100,
b = -4;
if (b < 0) {
@@ -384,159 +390,161 @@ if (b < 0) {
System.out.println(a + "+" + b + "=" + (a + b));
}</programlisting></td>
- <td valign="top"><screen>96=96</screen></td>
- </tr>
- </informaltable>
-
- <para>Since <code language="java">a</code> and <code
- language="java">b</code> are both variables of type <code
- language="java">int</code> they get added rather than string style
- concatenated. Resolving this issue may be effected by adding an
- empty string <coref
- linkend="sd1_qanda_betterSimpleMathEmptyString-1-co"/> forcing
- <xref linkend="glo_Java"/> to use the concatenation
- <quote>+</quote> operator in favour of the arithmetic one:</para>
+ <td valign="top"><screen>96=96</screen></td>
+ </tr>
+ </informaltable>
- <informaltable border="0">
- <tr>
- <th>Source code</th>
+ <para>Since <code language="java">a</code> and <code
+ language="java">b</code> are both variables of type <code
+ language="java">int</code> they get added rather than string
+ style concatenated. Resolving this issue may be effected by
+ adding an empty string <coref
+ linkend="sd1_qanda_betterSimpleMathEmptyString-1-co"/> forcing
+ <xref linkend="glo_Java"/> to use the concatenation
+ <quote>+</quote> operator in favour of the arithmetic
+ one:</para>
+
+ <informaltable border="0">
+ <tr>
+ <th>Source code</th>
- <th>Output</th>
- </tr>
+ <th>Output</th>
+ </tr>
- <tr>
- <td valign="top"><programlisting language="java">int a = 100,
+ <tr>
+ <td valign="top"><programlisting language="java">int a = 100,
b = -4;
if (b < 0) {
System.out.println(a + "" <co
- xml:id="sd1_qanda_betterSimpleMathEmptyString-1-co"/> + b+ "=" + (a + b));
+ xml:id="sd1_qanda_betterSimpleMathEmptyString-1-co"/> + b+ "=" + (a + b));
} else {
System.out.println(a + "+" + b + "=" + (a + b));
}</programlisting></td>
- <td valign="top"><screen>100-4=96</screen></td>
- </tr>
- </informaltable>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
+ <td valign="top"><screen>100-4=96</screen></td>
+ </tr>
+ </informaltable>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
- <qandaset defaultlabel="qanda" xml:id="sd1_qanda_booleanEqual">
- <title>Comparing for equality</title>
+ <qandaset defaultlabel="qanda" xml:id="sd1_qanda_booleanEqual">
+ <title>Comparing for equality</title>
- <qandadiv>
- <qandaentry>
- <question>
- <para>Copy the following snippet into your <xref
- linkend="glo_IDE"/>:</para>
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>Copy the following snippet into your <xref
+ linkend="glo_IDE"/>:</para>
- <programlisting language="java">int count = 1;
+ <programlisting language="java">int count = 1;
if (count = 4) { // is count equal to 4?
System.out.println("count is o.K.");
}</programlisting>
- <para>The <xref linkend="glo_Java"/> compiler will indicate an
- error:</para>
+ <para>The <xref linkend="glo_Java"/> compiler will indicate an
+ error:</para>
- <screen>Incompatible types.
+ <screen>Incompatible types.
Required: <emphasis role="red">boolean</emphasis>
Found: <emphasis role="red">int</emphasis></screen>
- <para>Explain its cause in detail by examining the underlying
- expression.</para>
-
- <tip>
- <para><xref linkend="glo_Java"/> provides two similar looking
- operators <code language="java">=</code> and <code
- language="java">==</code> having (totally) different
- semantics.</para>
- </tip>
- </question>
-
- <answer>
- <para>Java provides two seemingly similar but
- <emphasis>completely</emphasis> unrelated operators:</para>
-
- <glosslist>
- <glossentry>
- <glossterm><code language="java">=</code></glossterm>
-
- <glossdef>
- <para>This is being called the assignment operator. A
- typical statement reads <code language="java">a = 34</code>
- assigning the <code language="java">int</code> value <code
- language="java">34</code> to a variable <code
- language="java">a</code>.</para>
+ <para>Explain its cause in detail by examining the underlying
+ expression.</para>
- <para>Note this operator's semantics being completely
- different from even elementary math syntax. Consider:</para>
+ <tip>
+ <para><xref linkend="glo_Java"/> provides two similar looking
+ operators <code language="java">=</code> and <code
+ language="java">==</code> having (totally) different
+ semantics.</para>
+ </tip>
+ </question>
- <informalequation>
- <m:math display="block">
- <m:mrow>
- <m:mi>x</m:mi>
+ <answer>
+ <para>Java provides two seemingly similar but
+ <emphasis>completely</emphasis> unrelated operators:</para>
- <m:mo>=</m:mo>
+ <glosslist>
+ <glossentry>
+ <glossterm><code language="java">=</code></glossterm>
- <m:mi>y</m:mi>
- </m:mrow>
+ <glossdef>
+ <para>This is being called the assignment operator. A
+ typical statement reads <code language="java">a =
+ 34</code> assigning the <code language="java">int</code>
+ value <code language="java">34</code> to a variable <code
+ language="java">a</code>.</para>
+
+ <para>Note this operator's semantics being completely
+ different from even elementary math syntax.
+ Consider:</para>
+
+ <informalequation>
+ <m:math display="block">
+ <m:mrow>
+ <m:mi>x</m:mi>
- <m:mo>⇒</m:mo>
+ <m:mo>=</m:mo>
- <m:mrow>
- <m:msup>
- <m:mi>x</m:mi>
+ <m:mi>y</m:mi>
+ </m:mrow>
- <m:mi>2</m:mi>
- </m:msup>
+ <m:mo>⇒</m:mo>
- <m:mo>=</m:mo>
+ <m:mrow>
+ <m:msup>
+ <m:mi>x</m:mi>
- <m:msup>
- <m:mi>y</m:mi>
+ <m:mi>2</m:mi>
+ </m:msup>
- <m:mi>2</m:mi>
- </m:msup>
- </m:mrow>
- </m:math>
- </informalequation>
+ <m:mo>=</m:mo>
- <para>In math <quote>=</quote> denotes the equality of
- objects <abbrev>e.g.</abbrev> values, sets, functions and so
- on.</para>
- </glossdef>
- </glossentry>
+ <m:msup>
+ <m:mi>y</m:mi>
- <glossentry>
- <glossterm><code language="java">==</code></glossterm>
+ <m:mi>2</m:mi>
+ </m:msup>
+ </m:mrow>
+ </m:math>
+ </informalequation>
- <glossdef>
- <para>The comparison operator matching the usual math
- semantics comparing:</para>
+ <para>In math <quote>=</quote> denotes the equality of
+ objects <abbrev>e.g.</abbrev> values, sets, functions and
+ so on.</para>
+ </glossdef>
+ </glossentry>
- <itemizedlist>
- <listitem>
- <para><xref linkend="glo_Java"/> primitive types for
- equality of value.</para>
- </listitem>
+ <glossentry>
+ <glossterm><code language="java">==</code></glossterm>
- <listitem>
- <para><xref linkend="glo_Java"/> objects for
- identity.</para>
- </listitem>
- </itemizedlist>
- </glossdef>
- </glossentry>
- </glosslist>
+ <glossdef>
+ <para>The comparison operator matching the usual math
+ semantics comparing:</para>
+
+ <itemizedlist>
+ <listitem>
+ <para><xref linkend="glo_Java"/> primitive types for
+ equality of value.</para>
+ </listitem>
+
+ <listitem>
+ <para><xref linkend="glo_Java"/> objects for
+ identity.</para>
+ </listitem>
+ </itemizedlist>
+ </glossdef>
+ </glossentry>
+ </glosslist>
- <para>Thus <code language="java">(count = 4)</code> is an
- expression evaluating to 4. So the code in question may be
- re-written as:</para>
+ <para>Thus <code language="java">(count = 4)</code> is an
+ expression evaluating to 4. So the code in question may be
+ re-written as:</para>
- <programlisting language="java">int count = 1;
+ <programlisting language="java">int count = 1;
int countAssignment = (count = 4); // Assigning expression count = 4 to variable countAssignment
@@ -544,49 +552,49 @@ if (countAssignment) { <emphasis role="red">// Error: An int is not a boolean!</
System.out.println("count is o.K.");
}</programlisting>
- <para>Since the assignment operator is being evaluated from right
- to left we do not need braces:</para>
+ <para>Since the assignment operator is being evaluated from
+ right to left we do not need braces:</para>
- <programlisting language="java">...
+ <programlisting language="java">...
int countAssignment = count = 4; // Assigning expression count = 4 to variable countAssignment
...</programlisting>
- <para>This code is equivalent to its counterpart with respect to
- compilation. The comment <quote>is count equal to 4?</quote> is
- thus misleading: The intended comparison requires using the
- <quote>==</quote> operator rather than an assignment operator
- <quote>=</quote>. Changing it the resulting expression is indeed
- of type <code language="java">boolean</code>:</para>
+ <para>This code is equivalent to its counterpart with respect to
+ compilation. The comment <quote>is count equal to 4?</quote> is
+ thus misleading: The intended comparison requires using the
+ <quote>==</quote> operator rather than an assignment operator
+ <quote>=</quote>. Changing it the resulting expression is indeed
+ of type <code language="java">boolean</code>:</para>
- <programlisting language="java">int count = 4 + 3;
+ <programlisting language="java">int count = 4 + 3;
final boolean test = (count == 4); // Now using "==" (comparison) in favour of "=" (assignment)
System.out.println("test=" + test);</programlisting>
- <para>Again we may omit braces here:</para>
+ <para>Again we may omit braces here:</para>
- <programlisting language="java">...
+ <programlisting language="java">...
final boolean test = count == 4; // Now using "==" (comparison) in favour of "=" (assignment)
...</programlisting>
- <para>The <code language="java">boolean</code> variable <code
- language="java">test</code> will receive a value of <code
- language="java">false</code> as expected. Thus our initial code
- just needs a tiny modification replacing the assignment operator
- «<code language="java">=</code>» by the comparison operator «<code
- language="java">==</code>»:</para>
+ <para>The <code language="java">boolean</code> variable <code
+ language="java">test</code> will receive a value of <code
+ language="java">false</code> as expected. Thus our initial code
+ just needs a tiny modification replacing the assignment operator
+ «<code language="java">=</code>» by the comparison operator
+ «<code language="java">==</code>»:</para>
- <programlisting language="java">int count = 1;
+ <programlisting language="java">int count = 1;
if (count == 4) { // is count equal to 4?
System.out.println("count is o.K.");
}</programlisting>
- <note xml:id="sd1_note_useLiteralEqualsVariable">
- <para>In contrast to <xref linkend="glo_Java"/> some programming
- languages like C and C++ allow for integer values in <code
- language="java">if (...)</code> conditionals:</para>
+ <note xml:id="sd1_note_useLiteralEqualsVariable">
+ <para>In contrast to <xref linkend="glo_Java"/> some
+ programming languages like C and C++ allow for integer values
+ in <code language="java">if (...)</code> conditionals:</para>
- <programlisting language="c">#include <stdio.h>
+ <programlisting language="c">#include <stdio.h>
int main(int argc, char **args) {
@@ -596,63 +604,63 @@ int main(int argc, char **args) {
}
}</programlisting>
- <para>The integer expression <code language="java">count =
- 4</code> has got a value of 4. Integer values inside an <code
- language="java">if (...)</code> statement will be evaluated
- as:</para>
+ <para>The integer expression <code language="java">count =
+ 4</code> has got a value of 4. Integer values inside an <code
+ language="java">if (...)</code> statement will be evaluated
+ as:</para>
- <glosslist>
- <glossentry>
- <glossterm>true</glossterm>
+ <glosslist>
+ <glossentry>
+ <glossterm>true</glossterm>
- <glossdef>
- <para>if the expression's value differs from zero</para>
- </glossdef>
- </glossentry>
+ <glossdef>
+ <para>if the expression's value differs from zero</para>
+ </glossdef>
+ </glossentry>
- <glossentry>
- <glossterm>false</glossterm>
+ <glossentry>
+ <glossterm>false</glossterm>
- <glossdef>
- <para>if the expression's value equals zero</para>
- </glossdef>
- </glossentry>
- </glosslist>
+ <glossdef>
+ <para>if the expression's value equals zero</para>
+ </glossdef>
+ </glossentry>
+ </glosslist>
- <para>Thus in C and C++ the expression <code
- language="java">if(count = 4)</code> will always evaluate to
- <code language="java">true</code> irrespective of the variable
- <code language="java">count</code>'s initial value. Most
- important: The C compiler will not issue an error or warning
- unless non-default, more restrictive compile time warning
- options are being activated. Consider this widely used «feature»
- to be dangerous at best.</para>
-
- <para>For this reason it is good practice always using <code
- language="java">if (4 == count)</code> rather than <code
- language="java">if (count == 4)</code>: Even in C you cannot
- assign a value to a constant literal. Thus an accidentally
- mistyped <code language="java">if (4 = count)</code> statement
- will definitively result in a compile time error most likely
- saving its author from tedious debugging.</para>
- </note>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
+ <para>Thus in C and C++ the expression <code
+ language="java">if(count = 4)</code> will always evaluate to
+ <code language="java">true</code> irrespective of the variable
+ <code language="java">count</code>'s initial value. Most
+ important: The C compiler will not issue an error or warning
+ unless non-default, more restrictive compile time warning
+ options are being activated. Consider this widely used
+ «feature» to be dangerous at best.</para>
+
+ <para>For this reason it is good practice always using <code
+ language="java">if (4 == count)</code> rather than <code
+ language="java">if (count == 4)</code>: Even in C you cannot
+ assign a value to a constant literal. Thus an accidentally
+ mistyped <code language="java">if (4 = count)</code> statement
+ will definitively result in a compile time error most likely
+ saving its author from tedious debugging.</para>
+ </note>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
- <qandaset defaultlabel="qanda" xml:id="sd1_qanda_replaceElseIf">
- <title>Replacing <code language="java">else if (...){...}</code> by
- nested <code language="java">if ... else</code> statements</title>
+ <qandaset defaultlabel="qanda" xml:id="sd1_qanda_replaceElseIf">
+ <title>Replacing <code language="java">else if (...){...}</code> by
+ nested <code language="java">if ... else</code> statements</title>
- <qandadiv>
- <qandaentry>
- <question>
- <para>A computer newbie did not yet read about the <code
- language="java">else if(...)</code> branch construct but
- nevertheless tries to implement the following logic:</para>
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>A computer newbie did not yet read about the <code
+ language="java">else if(...)</code> branch construct but
+ nevertheless tries to implement the following logic:</para>
- <programlisting language="java">if (a < 7) {
+ <programlisting language="java">if (a < 7) {
System.out.println("o.K.");
} else if (b == 5) {
System.out.println("Maybe");
@@ -660,28 +668,28 @@ int main(int argc, char **args) {
System.out.println("Wrong!");
}</programlisting>
- <para><code language="java">a</code> and <code
- language="java">b</code> are supposed to be <code
- language="java">int</code> variables. Please help our newbie using
- just <code language="java">if(...){...} else {...} </code>
- avoiding <code language="java">else if(...) {}</code> branch
- statements!</para>
+ <para><code language="java">a</code> and <code
+ language="java">b</code> are supposed to be <code
+ language="java">int</code> variables. Please help our newbie
+ using just <code language="java">if(...){...} else {...} </code>
+ avoiding <code language="java">else if(...) {}</code> branch
+ statements!</para>
- <tip>
- <para>As the title suggests you may want to nest an
- <quote>inner</quote> <code language="java">if(...)</code> inside
- an <quote>outer</quote> one.</para>
- </tip>
- </question>
+ <tip>
+ <para>As the title suggests you may want to nest an
+ <quote>inner</quote> <code language="java">if(...)</code>
+ inside an <quote>outer</quote> one.</para>
+ </tip>
+ </question>
- <answer>
- <para>The solution requires replacing the <code
- language="java">else if(...)</code> branch by a nested <code
- language="java">if(...){ ...} else</code> statement and moving the
- final <code language="java">else</code> block into the nested
- one.</para>
+ <answer>
+ <para>The solution requires replacing the <code
+ language="java">else if(...)</code> branch by a nested <code
+ language="java">if(...){ ...} else</code> statement and moving
+ the final <code language="java">else</code> block into the
+ nested one.</para>
- <programlisting language="java">if (a < 7) {
+ <programlisting language="java">if (a < 7) {
System.out.println("o.K.");
} else {
if (b == 5) {
@@ -690,15 +698,15 @@ int main(int argc, char **args) {
System.out.println("Wrong!");
}
}</programlisting>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
- <figure xml:id="sd1_fig_IfOmitBlocks">
- <title>Single statement branches</title>
+ <figure xml:id="sd1_fig_IfOmitBlocks">
+ <title>Single statement branches</title>
- <programlisting language="java">double initialAmount = 3200;
+ <programlisting language="java">double initialAmount = 3200;
if (100000 <= initialAmount)
System.out.println("Interest:" + 1.2 * initialAmount / 100);
@@ -707,120 +715,120 @@ else if (1000 <= initialAmount)
else
System.out.println("Interest:" + 0);</programlisting>
- <para>Branches containing exactly one statement don't require a block
- definition.</para>
- </figure>
+ <para>Branches containing exactly one statement don't require a block
+ definition.</para>
+ </figure>
- <figure xml:id="sd1_fig_corporateSafety">
- <title>Aside: Corporate network security</title>
+ <figure xml:id="sd1_fig_corporateSafety">
+ <title>Aside: Corporate network security</title>
- <para>Would you access your online bank account using <emphasis
- role="bold">Stuttgart Media University's</emphasis> network?</para>
+ <para>Would you access your online bank account using <emphasis
+ role="bold">Stuttgart Media University's</emphasis> network?</para>
- <orderedlist>
- <listitem>
- <para>Yes</para>
- </listitem>
+ <orderedlist>
+ <listitem>
+ <para>Yes</para>
+ </listitem>
- <listitem>
- <para>Only on private equipment (Smartphone, tablet, laptop,
- ...)</para>
- </listitem>
+ <listitem>
+ <para>Only on private equipment (Smart phone, tablet, laptop,
+ ...)</para>
+ </listitem>
- <listitem>
- <para>Never!</para>
- </listitem>
- </orderedlist>
- </figure>
+ <listitem>
+ <para>Never!</para>
+ </listitem>
+ </orderedlist>
+ </figure>
- <figure xml:id="sd1_fig_onlineBanking">
- <title>Online banking</title>
+ <figure xml:id="sd1_fig_onlineBanking">
+ <title>Online banking</title>
- <mediaobject>
- <imageobject>
- <imagedata fileref="Ref/Statements/onlineBanking.svg"/>
- </imageobject>
- </mediaobject>
- </figure>
+ <mediaobject>
+ <imageobject>
+ <imagedata fileref="Ref/Statements/onlineBanking.svg"/>
+ </imageobject>
+ </mediaobject>
+ </figure>
- <figure xml:id="sd1_fig_ipSpoofing">
- <title>DNS Spoofing</title>
+ <figure xml:id="sd1_fig_ipSpoofing">
+ <title>DNS Spoofing</title>
- <mediaobject>
- <imageobject>
- <imagedata fileref="Ref/Statements/dns-spoofing.png"/>
- </imageobject>
- </mediaobject>
- </figure>
+ <mediaobject>
+ <imageobject>
+ <imagedata fileref="Ref/Statements/dns-spoofing.png"/>
+ </imageobject>
+ </mediaobject>
+ </figure>
- <figure xml:id="sd1_fig_getIpToDns">
- <title>Turn <xref linkend="glo_DNS"/> name into IP address</title>
+ <figure xml:id="sd1_fig_getIpToDns">
+ <title>Turn <xref linkend="glo_DNS"/> name into IP address</title>
- <informaltable border="0">
- <colgroup width="37%"/>
+ <informaltable border="0">
+ <colgroup width="37%"/>
- <colgroup width="63%"/>
+ <colgroup width="63%"/>
- <tr>
- <td valign="top"><screen>~> nslookup
+ <tr>
+ <td valign="top"><screen>~> nslookup
> server <emphasis role="red">141.62.1.5</emphasis> <co
- linkends="sd1_fig_getIpToDns-1"
- xml:id="sd1_fig_getIpToDns-1-co"/>
+ linkends="sd1_fig_getIpToDns-1"
+ xml:id="sd1_fig_getIpToDns-1-co"/>
Address: 141.62.1.5#53
>
> <emphasis role="red">meine.deutsche-bank.de</emphasis> <co
- linkends="sd1_fig_getIpToDns-2"
- xml:id="sd1_fig_getIpToDns-2-co"/>
+ linkends="sd1_fig_getIpToDns-2"
+ xml:id="sd1_fig_getIpToDns-2-co"/>
Server: 141.62.1.5
Address: 141.62.1.5#53
Non-authoritative answer:
Name: meine.deutsche-bank.de
Address: <emphasis role="red">129.35.230.2</emphasis> <co
- linkends="sd1_fig_getIpToDns-3"
- xml:id="sd1_fig_getIpToDns-3-co"/></screen></td>
-
- <td valign="top"><calloutlist>
- <callout arearefs="sd1_fig_getIpToDns-1-co" role="slideExclude"
- xml:id="sd1_fig_getIpToDns-1">
- <para>Nameserver answering <xref linkend="glo_DNS"/>
- queries.</para>
- </callout>
-
- <callout arearefs="sd1_fig_getIpToDns-2-co"
- xml:id="sd1_fig_getIpToDns-2">
- <para>Entering <xref linkend="glo_DNS"/> name.</para>
- </callout>
-
- <callout arearefs="sd1_fig_getIpToDns-3-co"
- xml:id="sd1_fig_getIpToDns-3">
- <para>IP address of <uri>meine.deutsche-bank.de</uri> is
- <code>129.35.230.2</code>.</para>
-
- <para>Caution: This IP value may become subject to
- tampering.</para>
- </callout>
- </calloutlist></td>
- </tr>
- </informaltable>
- </figure>
+ linkends="sd1_fig_getIpToDns-3"
+ xml:id="sd1_fig_getIpToDns-3-co"/></screen></td>
- <figure xml:id="sd1_fig_SSLCertificateError">
- <title><abbrev>SSL</abbrev> Certificate error</title>
+ <td valign="top"><calloutlist>
+ <callout arearefs="sd1_fig_getIpToDns-1-co"
+ role="slideExclude" xml:id="sd1_fig_getIpToDns-1">
+ <para>Nameserver answering <xref linkend="glo_DNS"/>
+ queries.</para>
+ </callout>
- <mediaobject>
- <imageobject>
- <imagedata fileref="Ref/Statements/sslCertificateError.svg"/>
- </imageobject>
- </mediaobject>
- </figure>
+ <callout arearefs="sd1_fig_getIpToDns-2-co"
+ xml:id="sd1_fig_getIpToDns-2">
+ <para>Entering <xref linkend="glo_DNS"/> name.</para>
+ </callout>
- <figure xml:id="sd1_fig_IfOmitBewareIndent">
- <title>The <link
- xlink:href="https://nakedsecurity.sophos.com/2014/02/24/anatomy-of-a-goto-fail-apples-ssl-bug-explained-plus-an-unofficial-patch/">Apple
- <quote><code>goto fail</code></quote> SSL bug</link></title>
+ <callout arearefs="sd1_fig_getIpToDns-3-co"
+ xml:id="sd1_fig_getIpToDns-3">
+ <para>IP address of <uri>meine.deutsche-bank.de</uri> is
+ <code>129.35.230.2</code>.</para>
- <programlisting language="c">static OSStatus SSLVerifySignedServerKeyExchange(SSLContext *ctx, bool isRsa,
+ <para>Caution: This IP value may become subject to
+ tampering.</para>
+ </callout>
+ </calloutlist></td>
+ </tr>
+ </informaltable>
+ </figure>
+
+ <figure xml:id="sd1_fig_SSLCertificateError">
+ <title><abbrev>SSL</abbrev> Certificate error</title>
+
+ <mediaobject>
+ <imageobject>
+ <imagedata fileref="Ref/Statements/sslCertificateError.svg"/>
+ </imageobject>
+ </mediaobject>
+ </figure>
+
+ <figure xml:id="sd1_fig_IfOmitBewareIndent">
+ <title>The <link
+ xlink:href="https://nakedsecurity.sophos.com/2014/02/24/anatomy-of-a-goto-fail-apples-ssl-bug-explained-plus-an-unofficial-patch/">Apple
+ <quote><code>goto fail</code></quote> SSL bug</link></title>
+
+ <programlisting language="c">static OSStatus SSLVerifySignedServerKeyExchange(SSLContext *ctx, bool isRsa,
SSLBuffer signedParams, uint8_t *signature, UInt16 signatureLen) {
OSStatus err;
...
@@ -838,51 +846,51 @@ fail:
SSLFreeBuffer(&signedHashes);
SSLFreeBuffer(&hashCtx);
return err; }</programlisting>
- </figure>
+ </figure>
- <figure xml:id="sd1_fig_appleSslBugCodeReachability">
- <title>Static code analysis</title>
+ <figure xml:id="sd1_fig_appleSslBugCodeReachability">
+ <title>Static code analysis</title>
- <informaltable border="0">
- <tr>
- <td><programlisting language="c">if ((err = SSLHashSHA1.update(...)) != 0)
+ <informaltable border="0">
+ <tr>
+ <td><programlisting language="c">if ((err = SSLHashSHA1.update(...)) != 0)
goto fail;
goto fail;</programlisting></td>
- <td>Reachable code, <code>err</code> yet 0</td>
- </tr>
+ <td>Reachable code, <code>err</code> yet 0</td>
+ </tr>
- <tr>
- <td><programlisting language="c">if ((err = SSLHashSHA1.final(...)) != 0)
+ <tr>
+ <td><programlisting language="c">if ((err = SSLHashSHA1.final(...)) != 0)
goto fail;
err = sslRawVerify(...); ...</programlisting></td>
- <td>Unreachable code: Variable <code language="java">err</code>
- unchanged.</td>
- </tr>
+ <td>Unreachable code: Variable <code language="java">err</code>
+ unchanged.</td>
+ </tr>
- <tr>
- <td><programlisting language="c">fail:
+ <tr>
+ <td><programlisting language="c">fail:
SSLFreeBuffer(&signedHashes);
SSLFreeBuffer(&hashCtx);
return err;</programlisting></td>
- <td>Reachable code, <code>err</code> possibly still 0</td>
- </tr>
- </informaltable>
- </figure>
+ <td>Reachable code, <code>err</code> possibly still 0</td>
+ </tr>
+ </informaltable>
+ </figure>
- <qandaset defaultlabel="qanda"
- xml:id="sd1_qanda_staticCodeAnalysisUnreachable">
- <title>Static code analysis</title>
+ <qandaset defaultlabel="qanda"
+ xml:id="sd1_qanda_staticCodeAnalysisUnreachable">
+ <title>Static code analysis</title>
- <qandadiv>
- <qandaentry>
- <question>
- <para>Consider the following snippet:</para>
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>Consider the following snippet:</para>
- <programlisting language="java">int count = 3;
+ <programlisting language="java">int count = 3;
count++;
if (count < 5)
@@ -891,52 +899,53 @@ if (count < 5)
System.out.println("Failed!");</programlisting>
- <para>This <xref linkend="glo_Java"/> code mimics the <link
- xlink:href="https://nakedsecurity.sophos.com/2014/02/24/anatomy-of-a-goto-fail-apples-ssl-bug-explained-plus-an-unofficial-patch/">Apple
- goto fail SSL bug</link>'s structural problem. Since <xref
- linkend="glo_Java"/> does not offer <code>goto</code> statements
- we use <code language="java">return</code> instead for terminating
- the <quote>current</quote> context.</para>
+ <para>This <xref linkend="glo_Java"/> code mimics the <link
+ xlink:href="https://nakedsecurity.sophos.com/2014/02/24/anatomy-of-a-goto-fail-apples-ssl-bug-explained-plus-an-unofficial-patch/">Apple
+ goto fail SSL bug</link>'s structural problem. Since <xref
+ linkend="glo_Java"/> does not offer <code>goto</code> statements
+ we use <code language="java">return</code> instead for
+ terminating the <quote>current</quote> context.</para>
- <para>Copy this code into your <xref linkend="glo_IDE"/>
- and:</para>
+ <para>Copy this code into your <xref linkend="glo_IDE"/>
+ and:</para>
- <orderedlist>
- <listitem>
- <para>Explain the resulting error. What is wrong? How do you
- correct this error?</para>
- </listitem>
+ <orderedlist>
+ <listitem>
+ <para>Explain the resulting error. What is wrong? How do you
+ correct this error?</para>
+ </listitem>
- <listitem>
- <para>Explain the <code language="java">count++</code>
- statement's purpose.</para>
+ <listitem>
+ <para>Explain the <code language="java">count++</code>
+ statement's purpose.</para>
- <tip>
- <para>There is no <quote>real</quote> application logic in
- the given code. It is an example meant to explain formal
- <xref linkend="glo_Java"/> language features. What happens
- if you correct the compile time error and in addition purge
- the <code language="java">count++</code> statement?</para>
- </tip>
- </listitem>
+ <tip>
+ <para>There is no <quote>real</quote> application logic in
+ the given code. It is an example meant to explain formal
+ <xref linkend="glo_Java"/> language features. What happens
+ if you correct the compile time error and in addition
+ purge the <code language="java">count++</code>
+ statement?</para>
+ </tip>
+ </listitem>
- <listitem>
- <para>What is the underlying idea of these warning and error
- messages?</para>
- </listitem>
- </orderedlist>
- </question>
+ <listitem>
+ <para>What is the underlying idea of these warning and error
+ messages?</para>
+ </listitem>
+ </orderedlist>
+ </question>
- <answer>
- <orderedlist>
- <listitem>
- <para>Like in the <link
- xlink:href="https://nakedsecurity.sophos.com/2014/02/24/anatomy-of-a-goto-fail-apples-ssl-bug-explained-plus-an-unofficial-patch/">Apple
- goto fail SSL bug</link> the code is poorly indented. Using
- your <xref linkend="glo_IDE"/>'s auto formatting feature
- (how?) you get:</para>
-
- <programlisting language="java">int count = 3;
+ <answer>
+ <orderedlist>
+ <listitem>
+ <para>Like in the <link
+ xlink:href="https://nakedsecurity.sophos.com/2014/02/24/anatomy-of-a-goto-fail-apples-ssl-bug-explained-plus-an-unofficial-patch/">Apple
+ goto fail SSL bug</link> the code is poorly indented. Using
+ your <xref linkend="glo_IDE"/>'s auto formatting feature
+ (how?) you get:</para>
+
+ <programlisting language="java">int count = 3;
count++;
if (count < 5)
@@ -945,20 +954,20 @@ return;
System.out.println("Failed!");</programlisting>
- <para>The second <code language="java">return</code> statement
- will leave the context unconditionally regardless of the
- preceding <code language="java">if (count < 5)</code> and
- the <code language="java">count</code> variable's value in
- particular. Thus the final <code
- language="java">System.out.println("Failed!")</code> <emphasis
- role="bold">can</emphasis> never be reached resulting in a
- compile time error.</para>
+ <para>The second <code language="java">return</code>
+ statement will leave the context unconditionally regardless
+ of the preceding <code language="java">if (count <
+ 5)</code> and the <code language="java">count</code>
+ variable's value in particular. Thus the final <code
+ language="java">System.out.println("Failed!")</code>
+ <emphasis role="bold">can</emphasis> never be reached
+ resulting in a compile time error.</para>
- <para>Removing the erroneous <code
- language="java">return</code> resolves the error leaving us
- with happily compiling code:</para>
+ <para>Removing the erroneous <code
+ language="java">return</code> resolves the error leaving us
+ with happily compiling code:</para>
- <programlisting language="java">int count = 3;
+ <programlisting language="java">int count = 3;
count++;
if (count < 5)
@@ -966,73 +975,74 @@ if (count < 5)
System.out.println("Failed!");</programlisting>
- <para>Conclusion: The <link
- xlink:href="https://nakedsecurity.sophos.com/2014/02/24/anatomy-of-a-goto-fail-apples-ssl-bug-explained-plus-an-unofficial-patch/">Apple
- goto fail SSL bug</link> could not have been occurring in
- <xref linkend="glo_Java"/> due to language features.</para>
- </listitem>
+ <para>Conclusion: The <link
+ xlink:href="https://nakedsecurity.sophos.com/2014/02/24/anatomy-of-a-goto-fail-apples-ssl-bug-explained-plus-an-unofficial-patch/">Apple
+ goto fail SSL bug</link> could not have been occurring in
+ <xref linkend="glo_Java"/> due to language features.</para>
+ </listitem>
- <listitem>
- <para>Removing <code language="java">count++</code> leaves us
- with:</para>
+ <listitem>
+ <para>Removing <code language="java">count++</code> leaves
+ us with:</para>
- <programlisting language="java">int count = 3;
+ <programlisting language="java">int count = 3;
if (count < 5) <co linkends="sd1_callout_staticIfAlwaysTrue-1"
- xml:id="sd1_callout_staticIfAlwaysTrue-1-co"/>
+ xml:id="sd1_callout_staticIfAlwaysTrue-1-co"/>
return;
System.out.println("Failed!");</programlisting>
- <calloutlist>
- <callout arearefs="sd1_callout_staticIfAlwaysTrue-1-co"
- xml:id="sd1_callout_staticIfAlwaysTrue-1">
- <para>Compiler warning: <emphasis role="bold">Condition
- 'count < 5' is always 'true'</emphasis>.</para>
- </callout>
- </calloutlist>
-
- <para>This warning is due to static compile time code
- analysis: The <code language="java">count</code> variable's
- value is not being altered throughout its scope. It could
- actually be declared as <code language="java">final int count
- = 3 disallowing sub</code>sequent assignments. Thus the <code
- language="java">return</code> inside <code language="java">if
- (count < 5)</code> will always be executed.</para>
-
- <para>Despite its simplicity having the count++ statement in
- place defeats the compiler's ability to discover that <code
- language="java">count</code> now having a value of 4 still
- being smaller than 5.</para>
- </listitem>
-
- <listitem>
- <para>The underlying idea is preventing programmers from
- coding carelessly: Even the <code language="java">if (count
- < 5)</code> statement is most likely an unintended
- bug.</para>
- </listitem>
- </orderedlist>
-
- <important>
- <para>Conclusion: Watch out for compiler warning messages and do
- not ignore them!</para>
-
- <para>In many cases compiler warnings reveal serious flaws.
- Correction on average will save you lots of cumbersome time
- debugging your code.</para>
- </important>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
+ <calloutlist>
+ <callout arearefs="sd1_callout_staticIfAlwaysTrue-1-co"
+ xml:id="sd1_callout_staticIfAlwaysTrue-1">
+ <para>Compiler warning: <emphasis role="bold">Condition
+ 'count < 5' is always 'true'</emphasis>.</para>
+ </callout>
+ </calloutlist>
+
+ <para>This warning is due to static compile time code
+ analysis: The <code language="java">count</code> variable's
+ value is not being altered throughout its scope. It could
+ actually be declared as <code language="java">final int
+ count = 3 disallowing sub</code>sequent assignments. Thus
+ the <code language="java">return</code> inside <code
+ language="java">if (count < 5)</code> will always be
+ executed.</para>
+
+ <para>Despite its simplicity having the count++ statement in
+ place defeats the compiler's ability to discover that <code
+ language="java">count</code> now having a value of 4 still
+ being smaller than 5.</para>
+ </listitem>
- <figure xml:id="sd1_fig_ifElseNested">
- <title>Nested <code language="java">if ... else</code></title>
+ <listitem>
+ <para>The underlying idea is preventing programmers from
+ coding carelessly: Even the <code language="java">if (count
+ < 5)</code> statement is most likely an unintended
+ bug.</para>
+ </listitem>
+ </orderedlist>
- <informaltable border="1">
- <tr>
- <td valign="top"><programlisting language="java">if ('A' == grade || 'B' == grade) {
+ <important>
+ <para>Conclusion: Watch out for compiler warning messages and
+ do not ignore them!</para>
+
+ <para>In many cases compiler warnings reveal serious flaws.
+ Correction on average will save you lots of cumbersome time
+ debugging your code.</para>
+ </important>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
+
+ <figure xml:id="sd1_fig_ifElseNested">
+ <title>Nested <code language="java">if ... else</code></title>
+
+ <informaltable border="1">
+ <tr>
+ <td valign="top"><programlisting language="java">if ('A' == grade || 'B' == grade) {
result = "Excellent";
} else {
if ('C' == grade) {
@@ -1046,22 +1056,26 @@ System.out.println("Failed!");</programlisting>
}
}</programlisting></td>
- <td valign="top"><mediaobject>
- <imageobject>
- <imagedata fileref="Ref/Statements/if_elseIf_else.svg"/>
- </imageobject>
- </mediaobject></td>
- </tr>
- </informaltable>
- </figure>
+ <td valign="top"><mediaobject>
+ <imageobject>
+ <imagedata fileref="Ref/Statements/if_elseIf_else.svg"/>
+ </imageobject>
+ </mediaobject></td>
+ </tr>
+ </informaltable>
+ </figure>
+ </section>
- <figure xml:id="sd1_fig_ifElse_else">
- <title>Equivalent: <code language="java">if ... else if ...
- else</code></title>
+ <section xml:id="sd1_sect_elseif">
+ <title>Using <code language="java">else if</code></title>
- <informaltable border="1">
- <tr>
- <td valign="top"><programlisting language="java">if ('A' == grade || 'B' == grade) {
+ <figure xml:id="sd1_fig_ifElse_else">
+ <title>Equivalent: <code language="java">if ... else if ...
+ else</code></title>
+
+ <informaltable border="1">
+ <tr>
+ <td valign="top"><programlisting language="java">if ('A' == grade || 'B' == grade) {
result = "Excellent";
} else if ('C' == grade) {
result = "O.k.";
@@ -1071,58 +1085,58 @@ System.out.println("Failed!");</programlisting>
result = "Failed";
}</programlisting></td>
- <td valign="top"><mediaobject>
- <imageobject>
- <imagedata fileref="Ref/Statements/if_elseIf_else.svg"/>
- </imageobject>
- </mediaobject></td>
- </tr>
- </informaltable>
- </figure>
+ <td valign="top"><mediaobject>
+ <imageobject>
+ <imagedata fileref="Ref/Statements/if_elseIf_else.svg"/>
+ </imageobject>
+ </mediaobject></td>
+ </tr>
+ </informaltable>
+ </figure>
- <figure xml:id="sd1_fig_ifElse_elseSyntax">
- <title><code language="java">if ... else if ... else</code>
- syntax</title>
+ <figure xml:id="sd1_fig_ifElse_elseSyntax">
+ <title><code language="java">if ... else if ... else</code>
+ syntax</title>
- <programlisting language="java">if (booleanExpression)
+ <programlisting language="java">if (booleanExpression)
(block | statement)
[else if (booleanExpression)
(block | statement) ]* <co linkends="sd1_fig_ifElse_elseSyntax-1"
- xml:id="sd1_fig_ifElse_elseSyntax-1-co"/>
+ xml:id="sd1_fig_ifElse_elseSyntax-1-co"/>
[else
(block | statement) ] <co linkends="sd1_fig_ifElse_elseSyntax-2"
- xml:id="sd1_fig_ifElse_elseSyntax-2-co"/></programlisting>
-
- <calloutlist role="slideExclude">
- <callout arearefs="sd1_fig_ifElse_elseSyntax-1-co"
- xml:id="sd1_fig_ifElse_elseSyntax-1">
- <para>The pair of braces [...] indicates an optional clause. The
- asterisk <quote>*</quote> indicates an arbitrary number of
- repetitions (zero to infinity).</para>
- </callout>
-
- <callout arearefs="sd1_fig_ifElse_elseSyntax-2-co"
- xml:id="sd1_fig_ifElse_elseSyntax-2">
- <para>The second pair of braces [...] again indicates an optional
- clause.</para>
-
- <para>Thus only the <quote><code language="java">if
- (booleanExpression) (block | statement)</code></quote> clause is
- mandatory.</para>
- </callout>
- </calloutlist>
- </figure>
+ xml:id="sd1_fig_ifElse_elseSyntax-2-co"/></programlisting>
+
+ <calloutlist role="slideExclude">
+ <callout arearefs="sd1_fig_ifElse_elseSyntax-1-co"
+ xml:id="sd1_fig_ifElse_elseSyntax-1">
+ <para>The pair of braces [...] indicates an optional clause. The
+ asterisk <quote>*</quote> indicates an arbitrary number of
+ repetitions (zero to infinity).</para>
+ </callout>
- <figure xml:id="sd1_fig_useScannerClass">
- <title>User input recipe</title>
+ <callout arearefs="sd1_fig_ifElse_elseSyntax-2-co"
+ xml:id="sd1_fig_ifElse_elseSyntax-2">
+ <para>The second pair of braces [...] again indicates an optional
+ clause.</para>
- <informaltable border="0">
- <colgroup width="64%"/>
+ <para>Thus only the <quote><code language="java">if
+ (booleanExpression) (block | statement)</code></quote> clause is
+ mandatory.</para>
+ </callout>
+ </calloutlist>
+ </figure>
- <colgroup width="36%"/>
+ <figure xml:id="sd1_fig_useScannerClass">
+ <title>User input recipe</title>
- <tr>
- <td valign="top"><programlisting language="java">import java.util.Scanner;
+ <informaltable border="0">
+ <colgroup width="64%"/>
+
+ <colgroup width="36%"/>
+
+ <tr>
+ <td valign="top"><programlisting language="java">import java.util.Scanner;
public class App {
public static void main(String[] args){
@@ -1139,41 +1153,41 @@ public class App {
}
}</programlisting></td>
- <td valign="top"><screen>Enter a value:123
+ <td valign="top"><screen>Enter a value:123
You entered 123</screen><para>See <methodname
- xlink:href="https://docs.oracle.com/javase/10/docs/api/java/util/Scanner.html#nextBoolean()">nextBoolean()</methodname>,
- <methodname><link
- xlink:href="https://docs.oracle.com/javase/10/docs/api/java/util/Scanner.html#nextByte()">nextByte()</link></methodname>
- and friends.</para></td>
- </tr>
- </informaltable>
- </figure>
+ xlink:href="https://docs.oracle.com/javase/10/docs/api/java/util/Scanner.html#nextBoolean()">nextBoolean()</methodname>,
+ <methodname><link
+ xlink:href="https://docs.oracle.com/javase/10/docs/api/java/util/Scanner.html#nextByte()">nextByte()</link></methodname>
+ and friends.</para></td>
+ </tr>
+ </informaltable>
+ </figure>
- <qandaset defaultlabel="qanda" xml:id="sw1QandaPostExamBonuspoints">
- <title>Post modifying an exam's marking</title>
+ <qandaset defaultlabel="qanda" xml:id="sw1QandaPostExamBonuspoints">
+ <title>Post modifying an exam's marking</title>
- <qandadiv>
- <qandaentry>
- <question>
- <para>After completely marking an examination a lecturer decides
- to globally add a number extra bonus points to a specific task .
- The task does have an upper limit of points to be awarded at
- maximum. We provide an example:</para>
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>After completely marking an examination a lecturer decides
+ to globally add a number extra bonus points to a specific task .
+ The task does have an upper limit of points to be awarded at
+ maximum. We provide an example:</para>
- <para>On completely fulfilling a given task 12 points will be
- awarded. So after marking the exam participants' points range from
- 0 to 12 points being represented by the variable <code
- language="java">pointsReached</code>.</para>
+ <para>On completely fulfilling a given task 12 points will be
+ awarded. So after marking the exam participants' points range
+ from 0 to 12 points being represented by the variable <code
+ language="java">pointsReached</code>.</para>
- <para>After completing his marking our lecturer wants to add three
- more points to all participants without breaching the 12 point
- limit.</para>
+ <para>After completing his marking our lecturer wants to add
+ three more points to all participants without breaching the 12
+ point limit.</para>
- <para>Complete the following code by assigning this modified
- number of points to the variable <code
- language="java">newResult</code>.</para>
+ <para>Complete the following code by assigning this modified
+ number of points to the variable <code
+ language="java">newResult</code>.</para>
- <programlisting language="java">public static void main(String[] args) {
+ <programlisting language="java">public static void main(String[] args) {
int pointsReached = 1;
int maximumPoints = 12;
@@ -1185,15 +1199,15 @@ You entered 123</screen><para>See <methodname
System.out.println("New Result:" + newResult);
}</programlisting>
- </question>
+ </question>
- <answer>
- <para>The basic task is to add up the values of <code
- language="java">pointsReached</code> and <code
- language="java">pointsToAdd</code>. When exceeding the limit we
- just assign the limit itself:</para>
+ <answer>
+ <para>The basic task is to add up the values of <code
+ language="java">pointsReached</code> and <code
+ language="java">pointsToAdd</code>. When exceeding the limit we
+ just assign the limit itself:</para>
- <programlisting language="java">public static void main(String[] args) {
+ <programlisting language="java">public static void main(String[] args) {
final int pointsReached = 1;
final int maximumPoints = 12;
@@ -1210,98 +1224,99 @@ You entered 123</screen><para>See <methodname
System.out.println("New Result:" + newResult);
}</programlisting>
- <para>This basically means calculating the minimum of the two
- expressions <code language="java">pointsReached +
- pointsToAdd</code> and <code language="java">maximumPoints</code>.
- This may as well be be implemented by:</para>
+ <para>This basically means calculating the minimum of the two
+ expressions <code language="java">pointsReached +
+ pointsToAdd</code> and <code
+ language="java">maximumPoints</code>. This may as well be be
+ implemented by:</para>
- <programlisting language="java">public static void main(String[] args) {
+ <programlisting language="java">public static void main(String[] args) {
final int pointsReached = 1;
final int maximumPoints = 12;
final int pointsToAdd = 3;
final int newResult = <link
- xlink:href="https://docs.oracle.com/javase/10/docs/api/java/lang/Math.html#min(int,int)">Math.min</link>(maximumPoints, pointsReached + pointsToAdd);
+ xlink:href="https://docs.oracle.com/javase/10/docs/api/java/lang/Math.html#min(int,int)">Math.min</link>(maximumPoints, pointsReached + pointsToAdd);
System.out.println("New Result:" + newResult);
}</programlisting>
- <para>You will fully understand the above expression <classname
- xlink:href="https://docs.oracle.com/javase/10/docs/api/java/lang/Math.html">Math</classname>.<methodname
- xlink:href="https://docs.oracle.com/javase/10/docs/api/java/lang/Math.html#min(int,int)">min(...)</methodname>
- after finishing the <quote>Static Final Variables</quote> section
- of <xref linkend="bib_Kurniawan"/>.</para>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
+ <para>You will fully understand the above expression <classname
+ xlink:href="https://docs.oracle.com/javase/10/docs/api/java/lang/Math.html">Math</classname>.<methodname
+ xlink:href="https://docs.oracle.com/javase/10/docs/api/java/lang/Math.html#min(int,int)">min(...)</methodname>
+ after finishing the <quote>Static Final Variables</quote>
+ section of <xref linkend="bib_Kurniawan"/>.</para>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
- <qandaset defaultlabel="qanda" xml:id="sd1QandaAtTheBar">
- <title>At the bar</title>
+ <qandaset defaultlabel="qanda" xml:id="sd1QandaAtTheBar">
+ <title>At the bar</title>
- <qandadiv>
- <qandaentry>
- <question>
- <para>This example uses existing program code to be explained
- later. You'll implement an interactive application which
- implements a dialogue with a user asking for input to be entered
- in a terminal like window as being shown in the following
- video:</para>
-
- <figure xml:id="sd1VideoUsingScannerClass">
- <title>Using a <classname
- xlink:href="https://docs.oracle.com/javase/10/docs/api/java/util/Scanner.html">Scanner</classname>
- class collecting user input.</title>
-
- <mediaobject>
- <videoobject>
- <videodata fileref="Ref/Video/scannerUsage.webm"/>
- </videoobject>
- </mediaobject>
- </figure>
-
- <para>A bar uses a software system for picking up orders. The bar
- will serve just orange juice and beer. For legal reasons the
- latter will only be served to persons of at least 16 years of age.
- We show three possible user dialogues:</para>
-
- <orderedlist>
- <listitem>
- <screen>On offer:
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>This example uses existing program code to be explained
+ later. You'll implement an interactive application which
+ implements a dialogue with a user asking for input to be entered
+ in a terminal like window as being shown in the following
+ video:</para>
+
+ <figure xml:id="sd1VideoUsingScannerClass">
+ <title>Using a <classname
+ xlink:href="https://docs.oracle.com/javase/10/docs/api/java/util/Scanner.html">Scanner</classname>
+ class collecting user input.</title>
+
+ <mediaobject>
+ <videoobject>
+ <videodata fileref="Ref/Video/scannerUsage.webm"/>
+ </videoobject>
+ </mediaobject>
+ </figure>
+
+ <para>A bar uses a software system for picking up orders. The
+ bar will serve just orange juice and beer. For legal reasons the
+ latter will only be served to persons of at least 16 years of
+ age. We show three possible user dialogues:</para>
+
+ <orderedlist>
+ <listitem>
+ <screen>On offer:
1=Beer
2=Orange juice
Your choice:>1
Tell me your age please:>15
Sorry, we are not allowed to serve beer to underage customers</screen>
- </listitem>
+ </listitem>
- <listitem>
- <screen>On offer:
+ <listitem>
+ <screen>On offer:
1=Beer
2=Orange juice
Your choice:>2
o.K.</screen>
- </listitem>
+ </listitem>
- <listitem>
- <screen>On offer:
+ <listitem>
+ <screen>On offer:
1=Beer
2=Orange juice
Your choice:>4
Sorry, invalid choice</screen>
- </listitem>
- </orderedlist>
+ </listitem>
+ </orderedlist>
- <para>Since you may not yet know how to enable <xref
- linkend="glo_Java"/> applications asking for user input simply use
- the following recipe to get started:</para>
+ <para>Since you may not yet know how to enable <xref
+ linkend="glo_Java"/> applications asking for user input simply
+ use the following recipe to get started:</para>
- <programlisting language="java"
- xml:id="sd1_listing_scannerBoilerplate">public static void main(String[] args) {
+ <programlisting language="java"
+ xml:id="sd1_listing_scannerBoilerplate">public static void main(String[] args) {
try (final Scanner scan = new Scanner(System.in)) { // Creating a scanner for reading user input
@@ -1314,21 +1329,22 @@ Sorry, invalid choice</screen>
} // Auto closing scanner
}</programlisting>
- <para>Copy this boilerplate code into your <xref
- linkend="glo_IDE"/>. The <xref linkend="glo_IDE"/> will assist you
- adding a required <code language="java">import
- java.util.Scanner;</code> statement in your code's header section.
- Execute this code. You should see a dialogue like:</para>
+ <para>Copy this boilerplate code into your <xref
+ linkend="glo_IDE"/>. The <xref linkend="glo_IDE"/> will assist
+ you adding a required <code language="java">import
+ java.util.Scanner;</code> statement in your code's header
+ section. Execute this code. You should see a dialogue
+ like:</para>
- <screen>Please enter a value:112
+ <screen>Please enter a value:112
You entered: 112</screen>
- <para>Then extend the above code implementing the desired
- behaviour.</para>
- </question>
+ <para>Then extend the above code implementing the desired
+ behaviour.</para>
+ </question>
- <answer>
- <programlisting language="java">package start;
+ <answer>
+ <programlisting language="java">package start;
import java.util.Scanner;
@@ -1363,41 +1379,41 @@ public class BarOrder {
scan.close();
}
}</programlisting>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
- <qandaset defaultlabel="qanda" xml:id="sd1QandaRomanNumeralsIf">
- <title>Roman numerals</title>
+ <qandaset defaultlabel="qanda" xml:id="sd1QandaRomanNumeralsIf">
+ <title>Roman numerals</title>
- <qandadiv>
- <qandaentry>
- <question>
- <para>Write an application which turns a positive integer values
- up to and including 10 into <link
- xlink:href="https://en.wikipedia.org/wiki/Roman_numerals">Roman
- numeral</link> representation:</para>
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>Write an application which turns a positive integer values
+ up to and including 10 into <link
+ xlink:href="https://en.wikipedia.org/wiki/Roman_numerals">Roman
+ numeral</link> representation:</para>
- <screen>Enter a number:>9
+ <screen>Enter a number:>9
IX</screen>
- <para>Regarding user input you may start from <xref
- linkend="sd1_listing_scannerBoilerplate"/> again. If the user
- enters a value smaller than one or greater than ten the following
- output is to be expected:</para>
+ <para>Regarding user input you may start from <xref
+ linkend="sd1_listing_scannerBoilerplate"/> again. If the user
+ enters a value smaller than one or greater than ten the
+ following output is to be expected:</para>
- <screen>Enter a number:>11
+ <screen>Enter a number:>11
Decimal value 11 not yet implemented</screen>
- <tip>
- <para>You may use a series of <code language="java">if () {...}
- else if () {...} ...</code> statements.</para>
- </tip>
- </question>
+ <tip>
+ <para>You may use a series of <code language="java">if ()
+ {...} else if () {...} ...</code> statements.</para>
+ </tip>
+ </question>
- <answer>
- <para><programlisting language="java">try (final Scanner scan = new Scanner(System.in)) {
+ <answer>
+ <para><programlisting language="java">try (final Scanner scan = new Scanner(System.in)) {
System.out.print("Enter a number:>");
final int number = scan.nextInt();
@@ -1426,74 +1442,74 @@ Decimal value 11 not yet implemented</screen>
System.out.println("Decimal value " + number + " not yet implemented");
}
}</programlisting></para>
- </answer>
- </qandaentry>
- </qandadiv>
- </qandaset>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
- <figure xml:id="sd1_fig_problemNumber2Dayname">
- <title>Converting numbers to day's names</title>
+ <figure xml:id="sd1_fig_problemNumber2Dayname">
+ <title>Converting numbers to day's names</title>
- <informaltable border="0">
- <colgroup width="28%"/>
+ <informaltable border="0">
+ <colgroup width="28%"/>
- <colgroup width="72%"/>
+ <colgroup width="72%"/>
- <tr>
- <td valign="top"><para>Task: Convert day's numbers to day's
- names</para></td>
+ <tr>
+ <td valign="top"><para>Task: Convert day's numbers to day's
+ names</para></td>
- <td valign="top"><informaltable border="1">
- <tr>
- <td>1</td>
+ <td valign="top"><informaltable border="1">
+ <tr>
+ <td>1</td>
- <td>Monday</td>
- </tr>
+ <td>Monday</td>
+ </tr>
- <tr>
- <td>2</td>
+ <tr>
+ <td>2</td>
- <td>Tuesday</td>
- </tr>
+ <td>Tuesday</td>
+ </tr>
- <tr>
- <td>3</td>
+ <tr>
+ <td>3</td>
- <td>Wednesday</td>
- </tr>
+ <td>Wednesday</td>
+ </tr>
- <tr>
- <td>4</td>
+ <tr>
+ <td>4</td>
- <td>Thursday</td>
- </tr>
+ <td>Thursday</td>
+ </tr>
- <tr>
- <td>5</td>
+ <tr>
+ <td>5</td>
- <td>Friday</td>
- </tr>
+ <td>Friday</td>
+ </tr>
- <tr>
- <td>6</td>
+ <tr>
+ <td>6</td>
- <td>Saturday</td>
- </tr>
+ <td>Saturday</td>
+ </tr>
- <tr>
- <td>7</td>
+ <tr>
+ <td>7</td>
- <td>Sunday</td>
- </tr>
- </informaltable></td>
- </tr>
- </informaltable>
- </figure>
+ <td>Sunday</td>
+ </tr>
+ </informaltable></td>
+ </tr>
+ </informaltable>
+ </figure>
- <figure xml:id="sd1_fig_dayNumber2NameByIfElseif">
- <title>Implementing number to day's names</title>
+ <figure xml:id="sd1_fig_dayNumber2NameByIfElseif">
+ <title>Implementing number to day's names</title>
- <programlisting language="java">try (final Scanner scan = new Scanner(System.in)) {
+ <programlisting language="java">try (final Scanner scan = new Scanner(System.in)) {
System.out.print("Enter a weekday number (1=Monday, 2=Tuesday,...) : ");
final int number = scan.nextInt();
@@ -1510,7 +1526,8 @@ Decimal value 11 not yet implemented</screen>
System.out.println("Invalid number " + number);
}
}</programlisting>
- </figure>
+ </figure>
+ </section>
</section>
<section xml:id="sd1_sect_switch">
--
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