线程的几个状态转换

java线程的几种状态转化图：

Java线程一共有七个状态，分别是新建（New），就绪（Ready to run），运行中（Running），睡眠（Sleeping），阻塞（Blocked），等待（Waiting），死亡（Dead/Terminate）

线程间的状态转化

1、新建（new）

新建一个线程，还未调用start方法

Thread t = new Thread();

2、就绪(runnable)

线程对象创建后，其他线程调用了该对象的start方法后，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)

可运行状态（Runnable）线程获得了cpu时间片（timeslice），执行程序代码

4、睡眠(sleeping)

也称TIME_WAITING（有等待时间的等待状态）

线程主动调用这几个方法：

1）Thread.sleep方法

2）object的wait方法 带有时间

3）Thread.join方法，带有时间

4）LockSupport的parkNanos方法，带有时间

5、阻塞(blocked)

阻塞状态是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状态，才有机会再次获得cpu timeslice转到运行状态，阻塞的情况有两种：

1）同步阻塞：运行的线程进入了一个sychronized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中

2）其他阻塞：运行的线程发出了IO请求时，JVM会把该线程置为阻塞状态，当IO处理完毕后，线程重新转入可运行状态

6、等待（waiting）

运行中的线程执行了4个方法中的任意方法：

1）Object的wait方法，并没有设置时间

2）Thread的join方法，并没有设置时间

3）Locksupport的park方法

4）Condition的wait方法

7、死亡（dead）

线程run方法、main方法执行结束，或者因为异常退出了run方法，则该线程结束生命周期。死亡线程不可复生。

/**
     * A thread state.  A thread can be in one of the following states: 
     * <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;
    }