Question

I have global static registry in my class, which registering instances in some circumstances. Actually it does not depend on garbage collecting, but some functionality is obviously placed in finalize().

During jUnit test I wish to test how this functionality works, but I can’t call GC by force. I am calling gc() in my tearDown()

@After
public void tearDown() throws Exception {

    log.debug("tearDown()");

    a = null;
    b = null;
    c = null;
    d = null;
    e = null;
    f = null;
    g = null;

    System.gc();

    log.debug("asserting hash size");
    assertEquals(0, Myclass.getRegisterSize());
}

but this does not help. I see in log that asserting message appears before finalizing.

Is it possible to wait until all finalizations occur?

Are there any other means, for example to restart classloader or flush heap or something in jUnit? I mean to do everything from scratch?

Answer 1

Not, it isn’t possible to wait for all finalizations to occur. They may not happen at all. Finalize gets run when the object is garbage collected. Some objects will never get collected, for instance a Main class. This doesn’t get garbage collected because the JVM exits before it runs the gc().

The best idea (really) is to add a method which does the cleaning up and then call it from your JUnit test. And, if you really, really need to, from finalize() as well. But you can never depend upon finalize() being called.