Two octal representation examples

Doc/Sd1/extraExercise.xml

@@ -27,6 +27,12 @@
           xlink:href="https://projecteuler.net/problem=1">1</link>, <link
           xlink:href="https://projecteuler.net/problem=2">2</link>, <link
           xlink:href="https://projecteuler.net/problem=4">4</link>, <link
+          xlink:href="https://projecteuler.net/problem=5">5</link>, <link
+          xlink:href="https://projecteuler.net/problem=8">8</link>, <link
+          xlink:href="https://projecteuler.net/problem=9">9</link>, <link
+          xlink:href="https://projecteuler.net/problem=1">1</link>, <link
+          xlink:href="https://projecteuler.net/problem=1">1</link>, <link
+          xlink:href="https://projecteuler.net/problem=1">1</link>, <link
           xlink:href="https://projecteuler.net/problem=1">1</link>, <link
           xlink:href="https://projecteuler.net/problem=1">1</link>, <link
           xlink:href="https://projecteuler.net/problem=1">1</link>, <link

Doc/Sd1/languageFundamentals.xml

@@ -1141,4 +1141,86 @@ System.out.println("New value=" + a);</programlisting>
       </qandadiv>
     </qandaset>
   </section>
+
+  <section xml:id="sd1fundamentalsWildThings">
+    <title>Wild things</title>
+
+    <qandaset defaultlabel="qanda" xml:id="sw1QandaWild">
+      <qandadiv>
+        <qandaentry>
+          <question>
+            <para>Consider the following program:</para>
+
+            <programlisting language="java">   public static void main(String[] args) {
+
+      int a = 20,
+          b = 3,
+          c = 9;
+      
+      System.out.println(a + " + " + b + " + " + c + " = " + (a + b + c));
+      
+   }</programlisting>
+
+            <para>This will run smoothly producing the expected output:</para>
+
+            <programlisting language="none">20 + 3 + 9 = 32</programlisting>
+
+            <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) {
+
+      int a = 20,
+          b = 03,
+          <emphasis role="bold">c = 09; // Compiler error: The literal 09 of type int is out of  range</emphasis>
+      
+      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>Explain the underlying cause of this error message. Why is
+            <code>b = 03</code> just fine in contrast to <code>c = 09</code>
+            ?</para>
+          </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>
+          </answer>
+        </qandaentry>
+      </qandadiv>
+    </qandaset>
+
+    <qandaset defaultlabel="qanda" xml:id="sd1OctalOutput">
+      <title>Strange output</title>
+
+      <qandadiv>
+        <qandaentry>
+          <question>
+            <para>Consider the following code:</para>
+
+            <programlisting language="java">   public static void main(String[] args) {
+
+      int a = 041;
+      System.out.println("Value = " + a);
+   }</programlisting>
+
+            <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>
+          </answer>
+        </qandaentry>
+      </qandadiv>
+    </qandaset>
+  </section>
 </chapter>