Are static fields open for garbage collection?

java static garbage-collection static-members
Michael Deardeuff picture Michael Deardeuff · Jan 17, 2009 · Viewed 47k times · Source

Given an hypothetical utility class that is used only in program setup:

class MyUtils {
   private static MyObject myObject = new MyObject();
   /*package*/static boolean doStuff(Params... params) {
       // do stuff with myObject and params...
   }
}

will myObject be garbage collected when it is no longer being used, or will it stick around for the life of the program?

Answer

bruno conde picture bruno conde · Jan 17, 2009

Static variables cannot be elected for garbage collection while the class is loaded. They can be collected when the respective class loader (that was responsible for loading this class) is itself collected for garbage.

Check out the JLS Section 12.7 Unloading of Classes and Interfaces

A class or interface may be unloaded if and only if its defining class loader may be reclaimed by the garbage collector [...] Classes and interfaces loaded by the bootstrap loader may not be unloaded.

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