BLOCKED - this state represents a thread which has been blocked and is waiting for a moniotor to enter/re-enter a synchronized block/method. A thread gets into this state after calling Object.wait method.
WAITING - this state represnts a thread in the waiting state and this wait is over only when some other thread performs some appropriate action. A thread can get into this state either by calling - Object.wait (without timeout), Thread.join (without timeout), or LockSupport.park methods.
BLOCKED是指线程正在等待获取锁；WAITING是指线程正在等待其他线程发来的通知（notify），收到通知后，可能会顺序向后执行（RUNNABLE），也可能会再次获取锁，进而被阻塞住（BLOCKED）。
PS:
notify与notifyAll的区别
notify是将某个waiting的线程状态改变为blocked(由于notify的线程尚未退出临界区，尚未释放锁，所以被唤醒的线程状态变为blocked)，notifyAll是将所有线程的状态改变为blocked。
