java学习-线程的6种状态，究其原码

线程的状态

关于线程的状态，又说6种状态，又说7种状态，原因是在JDK5之后，Ready和Running合称Runnable状态。

1. New 初始状态 ：在新建一个thread对象后，线程刚刚建立时
2. Ready就绪状态 ： 在线程调用start方法后，线程随时准备抢占时间片
3. Running 运行状态 ：在线程获取到cpu的时间片后，线程正在占用cpu资源
4. Time Waiting 限期等待状态 ：在线程调用sleep方法后，此线程进入休眠，在一定时间(sleep设定的时间)内，此线程处于限期等待
5. Waiting 无限期等待 ： 在一个线程one对象调用join后，one所在的线程 进入无限期等待，直到one运行完后，才参与抢占时间片
6. Blocked 阻塞状态 ： 在一个线程拿到锁标记进入同步代码块后，其他线程不能再进入同步代码块，进入阻塞，直到锁标记释放。
7. Terminated 终止状态（消亡状态）：在一个线程run内的语句全部结束后，线程终止。

原码

在Thread$State中，有一个枚举类型State，内写明了有6种线程状态。
在Trhead中，有getState（）方法，内容如下：

 public State getState() {
        // get current thread state
        return sun.misc.VM.toThreadState(threadStatus);
    }

返回线程的运行状态，在eclipse中 按ctrl+左键，进入State原码
查看此枚举类型如下：

 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;
    }