BLOCKED和WAITING的区别

/** * 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。