Question

If I have a reference pointing to some some java object, and do something like:

myObject=null;

Will the “lost data” of the old object be correctly freed by the JVM Garbage Collector? Something similar in C (with a pointer, would result in trash and a possible memory leak).
I am using null attribution in a java program and would like to now if it is “safe”.

Answer 1

Your assumption is correct, but you don’t usually need to specifically do that.

Let’s say your “myObject” is used in another object. At some point in the lifetime of your application’s execution, this object will stopped being referenced by any other object, and thus will be marked for deletion by the GC. Them myObject will be marked for deletion as well. As soon as all references to a given object disappear, the GC will eventually reclaim the memory.

There are (rare) exceptions, like event handling, where the dependency between two objects cannot be properly automatically ended, and you may end up with a memory leak: when you subscribe to an event on another class, then the subscriber cannot be collected even when there’s no “direct” references to it. In that specific case, it might be interesting to clear the link manually.