认识一下　java.util.concurrent.locks
转自http://download.oracle.com/javase/1.5.0/docs/guide/concurrency/overview.html

The java.util.concurrent.locks package provides a high-performance lock implementation with the same memory semantics as synchronization, but which also supports specifying a timeout when attempting to acquire a lock, multiple condition variables per lock, non-lexically scoped locks, and support for interrupting threads which are waiting to acquire a lock.