Garbage Collections

Q1:
class HappyGarbage01 
{ 
    public static void main(String args[]) 
    {
        HappyGarbage01 h = new HappyGarbage01(); 
        h.methodA(); /* Line 6 */
    } 
    Object methodA() 
    {
        Object obj1 = new Object(); 
        Object [] obj2 = new Object[1]; 
        obj2[0] = obj1; 
        obj1 = null; 
        return obj2[0]; 
    } 
}
Where will be the most chance of the garbage collector being invoked?

A After line 9

B After line 10

C After line 11

D Garbage collector never invoked in methodA()

Q2:
public class X 
{
    public static void main(String [] args) 
    {
        X x = new X();
        X x2 = m1(x); /* Line 6 */
        X x4 = new X();
        x2 = x4; /* Line 8 */
        doComplexStuff();
    }
    static X m1(X mx) 
    {
        mx = new X();
        return mx;
    }
}
After line 8 runs. how many objects are eligible for garbage collection?

A 0

B 1

C 2

D 3

Q3: What allows the programmer to destroy an object x?

A x.delete()

B x.finalize()

C Runtime.getRuntime().gc()

D Only the garbage collection system can destroy an object.

Q4:
class Test 
{  
    private Demo d; 
    void start() 
    {  
        d = new Demo(); 
        this.takeDemo(d); /* Line 7 */
    } /* Line 8 */
    void takeDemo(Demo demo) 
    { 
        demo = null;  
        demo = new Demo(); 
    } 
}
When is the Demo object eligible for garbage collection?

A After line 7

B After line 8

C After the start() method completes

D When the instance running this code is made eligible for garbage collection.

Q5:
void start() {  
    A a = new A(); 
    B b = new B(); 
    a.s(b);  
    b = null; /* Line 5 */
    a = null;  /* Line 6 */
    System.out.println('start completed'); /* Line 7 */
} 
When is the B object, created in line 3, eligible for garbage collection?

A after line 5

B after line 6

C after line 7

D There is no way to be absolutely certain.

Q6:
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 12

B after line 14

C after line 7, when doBar() completes

D after line 15, when main() completes

Q7:
public Object m() 
{  
    Object o = new Float(3.14F); 
    Object [] oa = new Object[l];
    oa[0] = o; /* Line 5 */
    o = null;  /* Line 6 */
    oa[0] = null; /* Line 7 */
    return o; /* Line 8 */
}
When is the Float object, created in line 3, eligible for garbage collection?

A just after line 5

B just after line 6

C just after line 7

D just after line 8

Q8:
class X2 
{
    public X2 x;
    public static void main(String [] args) 
    {
        X2 x2 = new X2();  /* Line 6 */
        X2 x3 = new X2();  /* Line 7 */
        x2.x = x3;
        x3.x = x2;
        x2 = new X2();
        x3 = x2; /* Line 11 */
        doComplexStuff();
    }
}

A 0

B 1

C 2

D 3


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