java - Garbage collection on a local variable

Question

I'm a C++ programmer entering the world of Java. And I cannot get rid of the bad feeling of having to let the Java garbage collector do my cleaning.

How, for example, will this code behave in Java?

public void myFunction() {
    myObject object = new myObject();
    object.doSomething();
}

Will the local variable object be deleted when myFunction() exits?

Do I have to set object to null before exiting, or will it be out of scope and be deleted by the GC? Or, at worst, will it leak like it would in C++?

Answer 1

It will be garbage collected at some point after it's no longer used. I believe in current implementations of Java it will actually persist until the end of the method, whereas the garbage collector in .NET is more aggressive. (I don't know whether there are any guarantees even in Java. Normally you'd only want the local variable to persist beyond its last possible read when you're debugging.)

But no, you don't need to set the variable to null, and doing so would harm readability.

It's unlikely that the object will garbage collected immediately after the method exits; it's up to when the GC runs... and of course if anything else holds onto a reference to the object, it may not be eligible for garbage collection anyway. Don't forget that the value of the variable is just a reference, not the object itself. (That may take a while to get used to coming from C++.)