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copied!<p>The child class does not maintain any special field representing its parent. You may be thinking something along the lines of inner classes, which <strong><em>do</em></strong> maintain a reference to their outer class. This is a special case and does not represent how super-sub classes relate to each other. </p> <p>Internally, the JVM maintains a 'method table', associating each class its loaded with the methods available for that class. The JVM also knows about the relationships between all classes its loaded, including super-sub relationships.</p> <p>When you invoke a <code>super</code> function, the JVM actually does a couple of things:</p> <ul> <li>Determines the parent of the class that the method is is being called from</li> <li>Determines the method on the parent that will be called</li> <li>Invokes the method, with a special instruction (<code>invokespecial</code>)</li> </ul> <p>If you were to examine the class file for your <code>Sub</code> class, you would see something like this for the <code>foo</code> method:</p> <pre><code>void foo(); flags: Code: stack=2, locals=1, args_size=1 0: aload_0 1: invokespecial #2 // Method Super.foo:()V 4: getstatic #3 // Field java/lang/System.out:Ljava/io/PrintStream; 7: ldc #4 // String Sub 9: invokevirtual #5 // Method java/io/PrintStream.println:(Ljava/lang/String;)V </code></pre> <p><em>Line 1 in the listing shows the special instruction that invokes the superclass method.</em></p> <p>A good source of reading would be the <a href="http://docs.oracle.com/javase/specs/jvms/se7/html/index.html" rel="nofollow">Java Virtual Machine Specification</a>, particularly <a href="http://docs.oracle.com/javase/specs/jvms/se7/html/jvms-2.html#jvms-2.11.8" rel="nofollow">Section 2.11.8</a>.</p>

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