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Asked: 2026-05-11T03:16:56+00:00

I was ‘forced’ to add myLocalVar = null; statement into finally clause just before

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I was ‘forced’ to add myLocalVar = null; statement into finally clause just before leaving method. Reason is to help GC. I was told I will get SMS’s during night when server crashes next time, so I better did it :-).

I think this is pointless, as myLocalVar is scoped to method, and will be ‘lost’ as soon as method exits. Extra nulling just pollutes the code, but is harmless otherwise.

My question is, where does this myth about helping GC come from? (I was referred to ‘Java memory books’) Do you know any article from ‘authorities’ which explain it in more depth? Is there possibility this is not a myth, but really helps somehow? If so, how? May nulling local variables cause any harm?

To clarify, method look like this:

void method() {   MyClass myLocalVar = null;   try {     myLocalVar = get reference to object;     ... do more here ...   } finally {     if (myLocalVar != null) {       myLocalVar.close(); // it is resource which we should close     }      myLocalVar = null; // THIS IS THE LINE I AM TALKING ABOUT   } }
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1 Answer

  1. There was an old piece of Sun documentation, Java Platform Performance (link sadly now broken, and I haven’t been able to find a new one), which described a situation where nulling a local variable which dropped out of scope actually had an effect on the GC.

    However, the paper referred to a very old version of java. As mentioned in this question (which also contains a précis of the problem described in the paper), this no longer affects current JVM implementations.

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