Garbage Collections

Q1:
class Bar { } 
class Test 
{  
    Bar doBar() 
    {
        Bar b = new Bar(); /* Line 6 */
        return b; /* Line 7 */
    } 
    public static void main (String args[]) 
    { 
        Test t = new Test();  /* Line 11 */
        Bar newBar = t.doBar();  /* Line 12 */
        System.out.println('newBar'); 
        newBar = new Bar(); /* Line 14 */
        System.out.println('finishing'); /* Line 15 */
    } 
}
At what point is the Bar object, created on line 6, eligible for garbage collection?

A after line 7, when doBar() completes

B after line 14

C after line 12

D after line 15, when main() completes

ANS:A - after line 12

Option B is correct. All references to the Bar object created on line 6 are destroyed when a new reference to a new Bar object is assigned to the variable newBar on line 14. Therefore the Bar object, created on line 6, is eligible for garbage collection after line 14. Option A is wrong. This actually protects the object from garbage collection. Option C is wrong. Because the reference in the doBar() method is returned on line 7 and is stored in newBar on line 12. This preserver the object created on line 6. Option D is wrong. Not applicable because the object is eligible for garbage collection after line 14.



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