Garbage collection of objects in loop in Java

Question

Q: 02 Given:

11. public void genNumbers() {
12.    ArrayList numbers = new ArrayList();
13.    for (int i=0; i<10; i++) {
14.       int value = i * ((int) Math.random());
15.       Integer intObj = new Integer(value);
16.       numbers.add(intObj);
17.    }
18.    System.out.println(numbers);
19. }

Which line of code marks the earliest point that an object referenced by intObj becomes a candidate for garbage collection?

A. Line 16
B. Line 17
C. Line 18
D. Line 19
E. The object is NOT a candidate for garbage collection.

Answer: D

Confused why answer is D not B. Please help me understand.

Why do you think it's B?

Maroun
– Maroun

2013-07-11 11:27:04 +00:00
Commented Jul 11, 2013 at 11:27 — Maroun
– Maroun, Commented Jul 11, 2013 at 11:27

André Stannek · Accepted Answer · 2013-07-11 11:29:32Z

8

You probably think since the variables lifetime is ended at the end of the block, the object can be removed by the garbage collector. But since that object was added to the list numbers, it is still referenced. Therefore it's after the lifetime of numbers ends and the list can also be removed by the garbage collector.

answered Jul 11, 2013 at 11:29

André Stannek

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Comments

Ingo · Accepted Answer · 2013-07-11 11:36:03Z

1

At line 17, the variable intObj goes out of scope, but this does only mean that there is one less reference to the Integer object than before. The numbersarray still references the same object as intObj did, so it cannot be collected before numbers goes out of scope.

answered Jul 11, 2013 at 11:36

Ingo

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Sainath Adepu · Accepted Answer · 2013-09-20 05:12:00Z

1

the object id garbage collected only when it is nolonger reachable by any reference. but in our example the new Integer(value); becomes out of rechable tointObj but it is accessed by arraylist so we still access the new Integer(value); so it becomes garbage collected only when arraylist becomes out of scope.

answered Sep 20, 2013 at 5:12

Sainath Adepu

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DevSolar · Accepted Answer · 2013-07-11 11:36:37Z

0

The object intObj is created at line 15, and a reference to it is added to numbers in line 16. While intObj goes out of scope at line 17, it is still referenced by numbers, which does not go out of scope until line 19.

answered Jul 11, 2013 at 11:36

DevSolar

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