Java大神Doug Lea对AQS的解析：Most synchronizers (locks, barriers, etc.) in the J2SE1.5
java.util.concurrent package are constructed using a small
framework based on class AbstractQueuedSynchronizer. This framework provides common mechanics for
atomically managing synchronization state, blocking and
unblocking threads, and queuing. The paper describes the
rationale, design, implementation, usage, and performance of this
framework.
