Explicit nulling

Question

In what situations in java is explicit nulling useful. Does it in any way assist the garbage collector by making objects unreachable or something? Is it considered to be a g

Answer 1

One special case I found it useful is when you have a very large object, and want to replace it with another large object. For example, look at the following code:

BigObject bigObject = new BigObject();
// ...
bigObject = new BigObject(); // line 3

If an instance of BigObject is so large that you can have only one such instance in the heap, line 3 will fail with OutOfMemoryError, because the 1st instance cannot be freed until the assignment instruction in line 3 completes, which is obviously after the 2nd instance is ready.

Now, if you set bigObject to null right before line 3:

bigObject = null;
bigObject = new BigObject(); // line 3

the 1st instance can be freed when JVM runs out of heap during the construction of the 2nd instance.