java8中线程的状态

java8中获取线程状态的方法是Thread.getState()，返回的是一个enum类型，具体定义如下：

public enum State {
/**
* Thread state for a thread which has not yet started.
*/
NEW,

/**
* Thread state for a runnable thread.  A thread in the runnable
* state is executing in the Java virtual machine but it may
* be waiting for other resources from the operating system
* such as processor.
*/
RUNNABLE,

/**
* 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:
* <ul>
*   <li>{@link Object#wait() Object.wait} with no timeout</li>
*   <li>{@link #join() Thread.join} with no timeout</li>
*   <li>{@link LockSupport#park() LockSupport.park}</li>
* </ul>
*
* <p>A thread in the waiting state is waiting for another thread to
* perform a particular action.
*
* For example, a thread that has called <tt>Object.wait()</tt>
* on an object is waiting for another thread to call
* <tt>Object.notify()</tt> or <tt>Object.notifyAll()</tt> on
* that object. A thread that has called <tt>Thread.join()</tt>
* is waiting for a specified thread to terminate.
*/
WAITING,

/**
* Thread state for a waiting thread with a specified waiting time.
* A thread is in the timed waiting state due to calling one of
* the following methods with a specified positive waiting time:
* <ul>
*   <li>{@link #sleep Thread.sleep}</li>
*   <li>{@link Object#wait(long) Object.wait} with timeout</li>
*   <li>{@link #join(long) Thread.join} with timeout</li>
*   <li>{@link LockSupport#parkNanos LockSupport.parkNanos}</li>
*   <li>{@link LockSupport#parkUntil LockSupport.parkUntil}</li>
* </ul>
*/
TIMED_WAITING,

/**
* Thread state for a terminated thread.
* The thread has completed execution.
*/
TERMINATED;
}

共有6个状态，下面是对这6个状态转换的简单总结。

1，NEW，Thread对象已经new出来了，还没有调用start方法。

2，RUNNABLE 调用了start()方法，线程进入可运行态，这里java没有区分线程正在执行还是在等待分配cpu时间片而在等待，统一被归为 RUNNABLE。

3，BLOCKED 阻塞态，通常与锁有关系，线程在等待持有一把锁相关的资源，比如进入同步块，获取ReentryLock等。

4，WAITING 等待状态，线程在等待另外一个线程来唤醒自己。比如另外的线程调用notify, notifyAll, 或者另外的线程终止（join方法会等待此条件）。

5，TIMED_WAITING 定时的等待，是对WAITING的一种细化，WAITING是无限期等待，而这里只会等待有限的时间。

6，TERMINATED 线程执行完任务，终止了。

从概念上来说，4、5两种状态可以合并来看，所以最终有5个不同的线程状态。