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    <p>Should be 2. The <code>main</code> function is static so it doesn't need an object.</p> <p><code>ClassA a</code> is an object and <code>ClassB b</code> is an object</p> <p><strong>EDIT</strong>: ClassB doesn't consist of two objects because extends is an <code>is-a</code> relationship and not a <code>has-a</code> relationship. (ta mik)</p> <p><strong>EDIT</strong>: There is also the <code>String[]</code> object that is created by the runtime system, and potentially any number of string objects place within that array. I am purposefully ignoring these but acknowledge their possible existence. (ta diveshpremdeep and Adam Goode)</p> <p><strong>FINAL EDIT</strong>: In order to determine how many objects are created (by the program, not the runtime system) you can use the <code>javap</code> program on the commandline like so (if test.java contains your example)</p> <pre><code>$ javac test.java $ javap -c ClassB </code></pre> <p>output:</p> <pre><code>Compiled from "test.java" class ClassB extends ClassA{ ClassB(); Code: 0: aload_0 1: invokespecial #1; //Method ClassA."&lt;init&gt;":()V 4: return public static void main(java.lang.String[]); Code: 0: new #2; //class ClassA 3: dup 4: invokespecial #1; //Method ClassA."&lt;init&gt;":()V 7: astore_1 8: new #3; //class ClassB 11: dup 12: invokespecial #4; //Method "&lt;init&gt;":()V 15: astore_2 16: return } </code></pre> <p>As you can see, there are only two bits of bytecode that are <code>new</code> (which creates objects I assume). One for class <code>ClassA</code> and the other for class <code>ClassB</code>. You can note that the <code>invokespecial</code> command is invoked afterwards to call the constructor, and also how class <code>ClassA</code>'s constructor is called from class <code>ClassB</code>'s constructor, but no new object is created inside the constructor (it is the default empty constructor).</p> <p>calling <code>javap -c ClassA</code> shows an equally boring constructor which invokes the constructor for Object.</p> <p>In summary: It is the <code>new</code> bytecode which creates objects on the heap, not the <code>invokespecial</code> which merely fills in the details of the memory allocated by the <code>new</code> bytecode.</p>
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    1. POhow many objects are created in the following code?
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    1. USbarkmadley
    1. USbarkmadley
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    1. POhow many objects are created in the following code?
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    1. CObut I think when creating object a,it will create a subobject with the type of Object,because it implicitly extends Object. The same as B.
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    2. CONo "subobjects" are created. ClassB is-a ClassA (but with extra B funkyness) rather has-a ClassA.
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      1. USMichael Lloyd Lee mlk
    3. COIf is as what you say, then by what way can I prove that the subobjects really do not exist or be created?
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