Thread Communication

Synchronization keeps two threads from stepping on each other when they touch the same data. Mutual exclusion alone isn't enough when threads need to coordinate. A consumer thread that finds an empty queue can't just keep spinning on a lock, checking if data has arrived. It needs to wait, get out of the way, and let a producer thread put something in. This chapter covers the tools Java's object monitors give you for that kind of coordination: wait, notify, and notifyAll. We'll walk through how they work, why they've to be called inside a synchronized block, the standard while (!condition) wait() pattern, and the producer-consumer problem they were designed for.