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Thread.State 首先看 JDK 中的代码: java.lang.Thread.State
/**
* A thread state. A thread can be in one of the following states:
* 一个线程的状态，一个线程可以处于以下状态中的某一个状态
* <ul>
* <li>{@link #NEW}<br>
* A thread that has not yet started is in this state.
* </li>
* <li>{@link #RUNNABLE}<br>
* A thread executing in the Java virtual machine is in this state.
* </li>
* <li>{@link #BLOCKED}<br>
* A thread that is blocked waiting for a monitor lock
* is in this state.
* </li>
* <li>{@link #WAITING}<br>
* A thread that is waiting indefinitely for another thread to
* perform a particular action is in this state.
* </li>
* <li>{@link #TIMED_WAITING}<br>
* A thread that is waiting for another thread to perform an action
* for up to a specified waiting time is in this state.
* </li>
* <li>{@link #TERMINATED}<br>
* A thread that has exited is in this state.
* </li>
* </ul>
*
* <p>
* A thread can be in only one state at a given point in time.
* These states are virtual machine states which do not reflect
* any operating system thread states.
*
* @since 1.5
* @see #getState
*/
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;
}
1、新建 (New) 新创建了一个线程对象，还未调用 start()方法。
2、就绪（Runnable）线程对象创建后，其他线程 (比如 main 线程）调用了该对象的 start() 方法。该状态的线程位于可运行线程池中，等待被线程调度选中 获取 cpu 的使用权。
3、运行中（Running，线程状态中并没有这一状态，但是实际执行中是有的）可运行状态 (runnable) 的线程获得了 cpu 时间片（timeslice），执行程序代码。
4、限期等待（Timed Waiting）也可以称作 TIMED_WAITING（有等待时间的等待状态）。
线程主动调用以下方法：
Thread.sleep 方法；
Object 的 wait 方法，带有时间；
Thread.join 方法，带有时间；
LockSupport 的 parkNanos 方法，带有时间。
5、无限期等待（Waiting）运行中（Running）的线程执行了以下方法：
Object 的 wait 方法，并且没有使用 timeout 参数;
Thread 的 join 方法，没有使用 timeout 参数；
LockSupport 的 park 方法；
Conditon 的 await 方法。
6、阻塞（Blocked）阻塞状态是指线程因为某种原因放弃了 cpu 使用权，暂时停止运行。直到线程进入可运行 (runnable) 状态，才有机会再次获得 cpu timeslice 转到运行 (running) 状态。阻塞的情况分两种：
同步阻塞：运行 (running) 的线程进入了一个 synchronized 方法，若该同步锁被别的线程占用，则 JVM 会把该线程放入锁池 (lock pool) 中。
其他阻塞：运行 (running) 的线程发出了 I / O 请求时，JVM 会把该线程置为阻塞状态。当 I / O 处理完毕时，线程重新转入可运行 (runnable) 状态。
7、结束（Terminated）线程 run()、main() 方法执行结束，或者因异常退出了 run()方法，则该线程结束生命周期。
线程状态探秘 jstack 查看线程状态 jstack -l <pid> 即可察看线程状态，如何使用呢？
随便写一个死循环看一下
public class TestThreadState {
public static void main(String[] args) {
for (; ;) {
}
}
}
ps -ef|grep TestThreadState，找到对应的 pid，jstack -l <pid> 即可，如果未输出线程信息，可以尝试使用 - F 参数来强制输出。
“main” #1 prio=5 os_prio=31 tid=0x00007f8194801800 nid=0x1603 runnable [0x000070000a9b4000]
java.lang.Thread.State: RUNNABLE
at org.java.bin.TestThreadState.main(TestThreadState.java:12)
