This is a generic question. So I'll give search tips rather than try answering that.
You HAVE to understand what threads are, what monitors are, and what wait and notify methods really do. You could start here
JavaWorld Article: Synchronizing Threads In Java which is probably one of the few articles that has any mention of a "potential monitor" to an object and implicitly distinguishes between an "object" and a "monitor".
These are the topics to google:
1. Java
Thread Synchronization
2. Java Thread Deadlock
3. Java Object Monitor
4. Java Thread Tutorial
If you like to explore further, search for articles on IBM developer works and Artima. Look up JSR 133.
Sun is a nice place to find BEGINNER articles and tutorials on any topics. Just append SUN to your search
string.
[ November 24, 2006: Message edited by: praveen balaji ]