Merge pull request #320 from habibasorour/issue_312_listing

Issue 312 fixed: listing in 6.5

Author: pearcej

source/ch6_definingclasses.ptx

@@ -782,11 +782,11 @@ public void test(Number a, Number b) {
 
         <p>
             The <c>Comparable</c> interface says that any object that claims to be <c>Comparable</c> must implement the <c>compareTo</c> method.
-            Here is an excerpt from <url href="https://docs.oracle.com/javase/7/docs/api/java/lang/Comparable.html#compareTo(T)" visual="https://docs.oracle.com/javase/7/docs/api/java/lang/Comparable.html#compareTo(T)">the official documentation</url> for the <c>compareTo</c> method as specified by the <c>Comparable</c> interface.
+            Here is an excerpt from <url href="https://docs.oracle.com/javase/7/docs/api/java/lang/Comparable.html#compareTo(T)" visual="https://docs.oracle.com/javase/7/docs/api/java/lang/Comparable.html#compareTo(T)">the official documentation</url> for the <c>compareTo</c> method as specified by the <c>Comparable</c> interface. <xref ref="java-comparable" text="type-global"/> shows the excerpt.
         </p>
 
-
-        <program  xml:id="java-comparable" language="text">
+        <listing xml:id="java-comparable">
+        <program language="text">
             <code>
 int compareTo(T o)
 Compares this object with the specified object for order. Returns a
@@ -798,27 +798,29 @@ iff y.compareTo(x) throws an exception.)
 ...
             </code>
         </program>
+        </listing>
 
         <p>
-            To make our <c>Fraction</c> class <c>Comparable</c> we must modify the class declaration line as follows:
+            To make our <c>Fraction</c> class <c>Comparable</c> we must modify the class declaration line as shown in <xref ref="java-make-comparable" text="type-global"/>.
         </p>
 
-
-        <program  xml:id="java-make-comparable"  language="java">
+        <listing xml:id="java-make-comparable">
+        <program language="java">
             <code>
 public class Fraction extends Number implements Comparable&lt;Fraction&gt; { // fraction class is a child of Number and implements the Comparable interface
     ...
 }
             </code>
         </program>
+        </listing>
 
         <p>
             The specification <c>Comparable&lt;Fraction&gt;</c> makes it clear that <c>Fraction</c> is only comparable with another <c>Fraction</c>.
-            The <c>compareTo</c> method could be implemented as follows:
+            The <c>compareTo</c> method could be implemented as shown in <xref ref="java-compare-to" text="type-global"/>.
         </p>
 
-
-        <program  xml:id="java-comparable2"  language="java">
+        <listing xml:id="java-compare-to">
+        <program language="java">
             <code>
 public int compareTo(Fraction other) { // compare this fraction with another fraction
     Integer num1 = this.numerator * other.getDenominator();
@@ -827,8 +829,11 @@ public int compareTo(Fraction other) { // compare this fraction with another fra
 }
             </code>
         </program>
+        </listing>
+
     </section>
 
+
     <section xml:id="static-member-variables">
         <title>Static member variables</title>