NULL is your friend 

If you set as much as you possibly can to NULL in sleep() you’ll get along with the JVM and Garbage Collector much better.

Additionally, on MacOSX, this is an even bigger win, because MacOSX has this three-stage lifecycle for objects. 

If you find yourself marking all of your instance variables NULL, consider making the component stateless. 

Copyright 2007, Pierce T. Wetter III