A lock may be associated with one or more conditions. These conditions are declared in the Condition interface. The purpose of these conditions is to allow threads to have control of a lock and check whether a condition is true or not. If it's false, the thread will be suspended until another thread wakes it up. The Condition interface provides the mechanisms to suspend a thread and wake up a suspended thread.

A classic problem in concurrent programming is the producer-consumer problem. We have a data buffer, one or more producers of data that save it in the buffer, and one or more consumers of data that take it from the buffer, as explained earlier in this chapter.

In this recipe, you will learn how to implement the producer-consumer problem using locks and conditions.