LockSupport
LockSupport类似Object的wait和notify方法:
// 1次unpark给线程1个许可
LockSupport.unpark(Thread.currentThread());
// 如果线程非阻塞重复调用没有任何效果
LockSupport.unpark(Thread.currentThread());
// 消耗1个许可
LockSupport.park(Thread.currentThread());
// 阻塞
LockSupport.park(Thread.currentThread());