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Garbage Collections Online Exam Quiz

Important questions about Garbage Collections. Garbage Collections MCQ questions with answers. Garbage Collections exam questions and answers for students and interviews.

1. At what point is the Bar object, created on line 6, eligible for garbage collection? 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 */ } }

Options

A : after line 12

B : after line 14

C : after line 7, when doBar() completes

D : after line 15, when main() completes

2. When is the B object, created in line 3, eligible for garbage collection? 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 */ }

Options

A : after line 5

B : after line 6

C : after line 7

D : There is no way to be absolutely certain.

3. What allows the programmer to destroy an object x?

Options

A : x.delete()

B : x.finalize()

C : Runtime.getRuntime().gc()

D : Only the garbage collection system can destroy an object.

4. When is the Demo object eligible for garbage collection? 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(); } }

Options

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.

5. After line 8 runs. how many objects are eligible for garbage collection? 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; } }

Options

A : 0

B : 1

C : 2

D : 3

6. After line 11 runs, how many objects are eligible for garbage collection? 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(); } }

Options

A : 0

B : 1

C : 2

D : 3

7. Where will be the most chance of the garbage collector being invoked? 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]; } }

Options

A : After line 9

B : After line 10

C : After line 11

D : Garbage collector never invoked in methodA()

8. When is the Float object, created in line 3, eligible for garbage collection? 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 */ }

Options

A : just after line 5

B : just after line 6

C : just after line 7

D : just after line 8

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