java线程中BLOCKED和WAITING有什么区别?

BLOCKED和WAITING有什么区别呢？
答复在JDK源码中可以找到，如下是Java.lang.Thread.State类的一部分注释。

/*** Thread state for a thread blocked waiting for a monitor lock.* A thread in the blocked state is waiting for a monitor lock* to enter a synchronized block/method or* reenter a synchronized block/method after calling* {@link Object#wait() Object.wait}.*/BLOCKED,/*** Thread state for a waiting thread.* A thread is in the waiting state due to calling one of the* following methods:* {@link Object#wait() Object.wait} with no timeout* {@link #join() Thread.join} with no timeout* {@link LockSupport#park() LockSupport.park}*** A thread in the waiting state is waiting for another thread to* perform a particular action.** For example, a thread that has called Object.wait()* on an object is waiting for another thread to call* Object.notify() or Object.notifyAll() on* that object. A thread that has called Thread.join()* is waiting for a specified thread to terminate.*/WAITING,

从中可以清晰的得到线程处于BLOCKED和WAITING状态的场景。
BLOCKED状态

线程处于BLOCKED状态的场景。

当前线程在等待一个monitor lock，比如等待执行synchronized代码块或者使用synchronized标记的方法。在synchronized块中循环调用Object类型的wait方法，如下是样例synchronized(this){while (flag){obj.wait();}// some other code}

WAITING状态

线程处于WAITING状态的场景。

调用Object对象的wait方法，但没有指定超时值。调用Thread对象的join方法，但没有指定超时值。调用LockSupport对象的park方法。

提到WAITING状态，顺便提一下TIMED_WAITING状态的场景。
TIMED_WAITING状态

线程处于TIMED_WAITING状态的场景。

调用Thread.sleep方法。调用Object对象的wait方法，指定超时值。调用Thread对象的join方法，指定超时值。调用LockSupport对象的parkNanos方法。调用LockSupport对象的parkUntil方法。