Java Programming/Destroying Objects

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Unlike in many other object-oriented programming languages, Java performs automatic garbage collection - any unreferenced objects are automatically erased from memory - and prohibits the user from manually destroying objects.

[edit] finalize()

When an object is garbage-collected, the programmer may want to manually perform cleanup, such as closing any open input/output streams. To accomplish this, the finalize() method is used. Note that finalize() should never be manually called, except to call a super class' finalize method from a derived class' finalize method. Also, we can not rely on when the finalize() method will be called. If the java application exits before the object is garbage-collected, the finalize() method may never be called.

protected void finalize() throws Throwable 
{
    try {
        doCleanup();        // Perform some cleanup.  If it fails for some reason, it is ignored.
    } finally {
        super.finalize(); //Call finalize on the parent object
    }
}

The garbage-collector thread runs in a lower priority than the other threads. If the application creates objects faster than the garbage-collector can claim back memory, the program can run out of memory.