Is it a good practice to remove references to help the GC?

Question

I am wondering whether you would consider it a good practice to remove references (setting them to null) to objects in order to help the Java Garbage Collector.

For instance, let's say you have a class with two fields, one of them being very memory-consuming. If you know you only need it for a particular processing, you can null it right after to help the GC.

Assume I really need those two to be fields, and not only internal variables, so heavyObject1 cannot be out of scope at the end of the method.

Would you do this as a general practice?

public class TestClass {

   public static Object heavyObject1;
   public static Object object2;

   private static void action() {
    object2 = doSomething(heavyObject1);

    heavyObject1 = null; //is this good?
   }
}

Answer 1

Usually it isn't needed.

It's a good idea in the following specific circumstance:

• The object is large (i.e. large enough for you to care)
• You are sure the object won't be needed again
• The object won't go out of scope otherwise (e.g. you know the surrounding object won't be garbage collected)

However if you find yourself in this situation I suspect you have a design smell anyway: why does the internal object have such a different scope / lifetime from the enclosing object? This makes me suspicious, because usually when you build up an object graph with composition you expect the composed objects to have similar lifetimes.

Answer 2

In most of the cases, you dont need to set the object to null to be garbage collected.If you decalre the object in proper scope(method level,instance level or class level), the object will be unreachable immediately after its use and will be eligible for garbage collection.