diff --git a/Doc/Sd1/statements.xml b/Doc/Sd1/statements.xml
index feccfc98fe40d02e34a3f480cb664e6f5979df76..fcc4019658b7781b2ed0881b9bd06ad26eb7e0be 100644
--- a/Doc/Sd1/statements.xml
+++ b/Doc/Sd1/statements.xml
@@ -457,8 +457,8 @@ if (count = 4) { // is count equal to 4?
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>
+ <para>Explain its cause in detail by examining the <code
+ language="java">count = 4</code> expression.</para>
<tip>
<para><xref linkend="glo_Java"/> provides two similar looking
@@ -469,8 +469,9 @@ Found: <emphasis role="red">int</emphasis></screen>
</question>
<answer>
- <para>Java provides two seemingly similar but
- <emphasis>completely</emphasis> unrelated operators:</para>
+ <para>The two operators <code language="java">=</code> and <code
+ language="java">==</code> are <emphasis>completely</emphasis>
+ unrelated:</para>
<glosslist>
<glossentry>
@@ -520,6 +521,13 @@ Found: <emphasis role="red">int</emphasis></screen>
<para>In math <quote>=</quote> denotes the equality of
objects <abbrev>e.g.</abbrev> values, sets, functions and
so on.</para>
+
+ <para>More formally the expression <code
+ language="java">count = 4</code> is of type <code
+ language="java">int</code> evaluating to 4 (surprise!).
+ However an <code language="java">if (...)</code> operates
+ on <code language="java">boolean</code> values only. We
+ thus must not supply expressions of any other type.</para>
</glossdef>
</glossentry>
@@ -541,17 +549,22 @@ Found: <emphasis role="red">int</emphasis></screen>
identity.</para>
</listitem>
</itemizedlist>
+
+ <para>In particular an expression like <code
+ language="java">count == 4</code> is of type boolean:
+ Either <code language="java">true</code> or <code
+ language="java">false</code>.</para>
</glossdef>
</glossentry>
</glosslist>
- <para>Thus <code language="java">(count = 4)</code> is an
+ <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;
-int countAssignment = (count = 4); // Assigning expression count = 4 to variable countAssignment
+int countAssignment = (count = 4); // Assigning expression count = 4 to variable countAssignment.
if (countAssignment) { <emphasis role="red">// Error: An int is not a boolean!</emphasis>
System.out.println("count is o.K.");
@@ -677,8 +690,8 @@ int main(int argc, char **args) {
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>
+ avoiding <code language="java"><emphasis role="red">else
+ if</emphasis>(...) {}</code> branch statements!</para>
<tip>
<para>As the title suggests you may want to nest an
@@ -690,9 +703,9 @@ int main(int argc, char **args) {
<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>
+ language="java">if(...){ ...} else {...}</code> statement by
+ moving the final <code language="java">else</code> block into
+ the nested one.</para>
<programlisting language="java">if (a < 7) {
System.out.println("o.K.");
@@ -1026,19 +1039,86 @@ You entered 123</screen><para>See <methodname
<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>A lecturer marks an exam having a maximum of 12 reachable
+ points:</para>
+
+ <informaltable border="1" width="50%">
+ <tr>
+ <th>Name</th>
+
+ <th>Mark</th>
+ </tr>
+
+ <tr>
+ <td>Aaron</td>
+
+ <td>3</td>
+ </tr>
- <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>
+ <tr>
+ <td>Maureen</td>
+
+ <td>11</td>
+ </tr>
- <para>After completing his marking our lecturer wants to add
- three more points to all participants without breaching the 12
- point limit.</para>
+ <tr>
+ <td>Sally</td>
+
+ <td>1</td>
+ </tr>
+
+ <tr>
+ <td>...</td>
+
+ <td>...</td>
+ </tr>
+ </informaltable>
+
+ <para>The lecturer is dissatisfied with the overall result. He
+ wants to add 3 bonus points but still keeping the maximum of 12
+ points to be reachable:</para>
+
+ <informaltable border="1" width="50%">
+ <tr>
+ <th>Name</th>
+
+ <th>Mark</th>
+
+ <th>3 bonus points augmented mark</th>
+ </tr>
+
+ <tr>
+ <td>Aaron</td>
+
+ <td>3</td>
+
+ <td>6</td>
+ </tr>
+
+ <tr>
+ <td>Maureen</td>
+
+ <td>11</td>
+
+ <td><emphasis role="red">12</emphasis></td>
+ </tr>
+
+ <tr>
+ <td>Sally</td>
+
+ <td>1</td>
+
+ <td>4</td>
+ </tr>
+
+ <tr>
+ <td>...</td>
+
+ <td>...</td>
+
+ <td>...</td>
+ </tr>
+ </informaltable>
<para>Complete the following code by assigning this modified
number of points to the variable <code
@@ -1046,15 +1126,17 @@ You entered 123</screen><para>See <methodname
<programlisting language="java">public static void main(String[] args) {
- int pointsReached = 1;
- int maximumPoints = 12;
- int pointsToAdd = 3;
+ int mark = 1; // May range from 0 to 12 points
+
- final int newResult;
+ final int maximumPoints = 12;
+ final int pointsToAdd = 3;
- // TODO: Assignment to variable newResult
+ final int augmentedMark;
- System.out.println("New Result:" + newResult);
+ // TODO: Assignment to variable augmentedMark
+
+ System.out.println("New marking:" + augmentedMark);
}</programlisting>
</question>
@@ -1070,22 +1152,21 @@ You entered 123</screen><para>See <methodname
final int maximumPoints = 12;
final int pointsToAdd = 3;
- final int newResult;
+ final int augmentedMark;
if (maximumPoints <= pointsReached + pointsToAdd) {
- newResult = maximumPoints;
+ augmentedMark = maximumPoints;
} else {
- newResult = pointsReached + pointsToAdd;
+ augmentedMark = pointsReached + pointsToAdd;
}
- System.out.println("New Result:" + newResult);
+ System.out.println("New marking:" + augmentedMark);
}</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>The augmented marks equal the minimum of <code
+ language="java">(pointsReached + pointsToAdd</code>) and <code
+ language="java">maximumPoints</code>. We may thus code as
+ well:</para>
<programlisting language="java">public static void main(String[] args) {
@@ -1093,10 +1174,10 @@ You entered 123</screen><para>See <methodname
final int maximumPoints = 12;
final int pointsToAdd = 3;
- final int newResult = <link
+ final int augmentedMark = <link
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);
+ System.out.println("New Result:" + augmentedMark);
}</programlisting>
<para>You will fully understand the above expression <classname
@@ -1650,14 +1731,16 @@ Tuesday</screen>
</question>
<answer>
- <para>With respect to <xref linkend="sd1_fig_switch"/> a small
- modification is being required</para>
+ <para>With respect to <xref linkend="sd1_fig_switch"/> two
+ modification are being required:</para>
- <programlisting language="java">...
-switch(day % 7) {
+ <programlisting language="none">...
+switch(<emphasis role="red">day % 7</emphasis>) {
case 1: System.out.println("Monday"); break;
case 2: System.out.println("Tuesday"); break;
-...</programlisting>
+ ...
+ <emphasis role="red">case 0</emphasis>: System.out.println("Sunday"); break;
+}</programlisting>
</answer>
</qandaentry>
</qandadiv>
@@ -1709,8 +1792,10 @@ Unknown day name 'July'</screen>
<tip>
<orderedlist>
<listitem>
- <para>Starting from <xref linkend="glo_Java"/> 7 switch
- statements using strings are allowed.</para>
+ <para>Starting from <xref linkend="glo_Java"/> 7 <classname
+ xlink:href="https://docs.oracle.com/en/java/javase/14/docs/api/java.base/java/lang/String.html">String</classname>
+ based <code language="java">switch</code> statements are
+ allowed.</para>
</listitem>
<listitem>
@@ -1815,12 +1900,16 @@ Midweek</screen>
final String day = scan.next();
switch(day) {
case "Monday": System.out.println("Start of work week"); break;
+
case "Tuesday":
case "Wednesday":
case "Thursday": System.out.println("Midweek"); break;
+
case "Friday": System.out.println("End of work week"); break;
+
case "Saturday":
case "Sunday": System.out.println("Weekend"); break;
+
default: System.out.println("Unknown day name " + day); break;
}
}</programlisting>
@@ -1905,20 +1994,21 @@ public class LeapYear {
public static void main(String[] args) {
- final Scanner scan = new Scanner(System.in); // Read user input
- System.out.print("Enter a year:>");
- final int year = scan.nextInt();
- scan.close();
-
- if (0 == year % 400) { <emphasis role="bold"> // Every 400 years we do have a leap year.</emphasis>
- System.out.println(
- "Year " + year + " is a leap year");
- } else if (0 == year % 4 && <emphasis role="bold"> // Every 4 years we do have a leap year</emphasis>
- 0 != year % 100) { <emphasis role="bold"> // unless year is a multiple of 100.</emphasis>
- System.out.println("Year " + year + " is a leap year");
- } else {
- System.out.println("Year " + year + " is no leap year");
- }
+ try (final Scanner scan = new Scanner(System.in)) {
+
+ System.out.print("Enter a year:>");
+ final int year = scan.nextInt();
+
+ if (0 == year % 400) { <emphasis role="bold"> // Every 400 years we do have a leap year.</emphasis>
+ System.out.println(
+ "Year " + year + " is a leap year");
+ } else if (0 == year % 4 && <emphasis role="bold"> // Every 4 years we do have a leap year</emphasis>
+ 0 != year % 100) { <emphasis role="bold"> // unless year is a multiple of 100.</emphasis>
+ System.out.println("Year " + year + " is a leap year");
+ } else {
+ System.out.println("Year " + year + " is no leap year");
+ }
+ }
}
}</programlisting>
@@ -1929,12 +2019,7 @@ public class LeapYear {
branch into one resolves the issue:</para>
<programlisting language="java">public static void main(String[] args) {
-
- final Scanner scan = new Scanner(System.in); // Read user input
- System.out.print("Enter a year:>");
- final int year = scan.nextInt();
- scan.close();
-
+ ...
if (0 == year % 400 || <emphasis role="bold">// Every 400 years we do have a leap year.</emphasis>
(0 == year % 4 && <emphasis role="bold">// Every 4 years we do have a leap year</emphasis>
0 != year % 100)) { <emphasis role="bold">// unless year is a multiple of 100.</emphasis>
@@ -1942,20 +2027,20 @@ public class LeapYear {
} else {
System.out.println("Year " + year + " is no leap year");
}
-}</programlisting>
+...</programlisting>
<para>Some enthusiasts prefer compact expressions at the expense
- of readability («Geek syndrome»). The following code is fully
- equivalent albeit syntactically different:</para>
+ of readability (<quote>Geek syndrome</quote>) sometimes referred
+ to as <quote>syntactic sugar</quote>. The following code based on
+ the <code language="java"
+ xlink:href="https://www.geeksforgeeks.org/java-ternary-operator-with-examples">...?
+ ...: ...</code> operator is fully equivalent:</para>
- <programlisting language="java">final Scanner scan = new Scanner(System.in); // Read user input
-System.out.print("Enter a year:>");
-final int year = scan.nextInt();
+ <programlisting language="java">...
System.out.println("Year " + year +
(year % 400 == 0 || year % 4 == 0 && 0 != year % 100 ? " is a leap year" : " is no leap year"));
-
-scan.close();</programlisting>
+}</programlisting>
</answer>
</qandaentry>
</qandadiv>
@@ -2102,12 +2187,104 @@ Do not copy!</screen></td>
<programlisting language="java">int threeSeries = 1;
-while ((threeSeries *=3) < 100);
+while ((threeSeries *=3 ) < 100);
System.out.println(threeSeries);</programlisting>
<para>Exercise: Guess resulting output.</para>
</figure>
+
+ <qandaset defaultlabel="qanda" xml:id="sd1_statements_qanda_factorial">
+ <title>Calculating factorial</title>
+
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>The factorial <inlineequation>
+ <m:math display="inline">
+ <m:mrow>
+ <m:mi>n</m:mi>
+
+ <m:mo>!</m:mo>
+ </m:mrow>
+ </m:math>
+ </inlineequation> of a given integer n is being defined as the
+ following product:</para>
+
+ <informalequation>
+ <m:math display="block">
+ <m:mrow>
+ <m:mrow>
+ <m:mi>n</m:mi>
+
+ <m:mo>!</m:mo>
+ </m:mrow>
+
+ <m:mo>=</m:mo>
+
+ <m:mrow>
+ <m:mi>n</m:mi>
+
+ <m:mo>×</m:mo>
+
+ <m:mrow>
+ <m:mo>(</m:mo>
+
+ <m:mrow>
+ <m:mi>n</m:mi>
+
+ <m:mo>-</m:mo>
+
+ <m:mi>1</m:mi>
+ </m:mrow>
+
+ <m:mo>)</m:mo>
+ </m:mrow>
+
+ <m:mo>×</m:mo>
+
+ <m:mo>⋯</m:mo>
+
+ <m:mo>×</m:mo>
+
+ <m:mi>2</m:mi>
+
+ <m:mo>×</m:mo>
+
+ <m:mi>1</m:mi>
+ </m:mrow>
+ </m:mrow>
+ </m:math>
+ </informalequation>
+
+ <para>Write an application asking a user for an integer value
+ and calculate the corresponding factorial e.g.:</para>
+
+ <screen>Enter an integer value: 5
+5! == 120</screen>
+ </question>
+
+ <answer>
+ <programlisting language="java">public static void main(String[] args) {
+ try (final Scanner scan = new Scanner(System.in)) {
+
+ System.out.print("Enter an integer value: ");
+ final int value = scan.nextInt();
+
+ long factorial = value;
+ int i = value;
+
+ while (1 < --i) {
+ factorial *= i;
+ }
+
+ System.out.println(value + "! == " + factorial);
+ }
+}</programlisting>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
</section>
<section xml:id="sd1_sect_doWhile">