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线程状态
- NEW
- RUNNABLE
- BLOCKED
- WAITING
- TIMED_WAITING
- TERMINATED
参考JDK源码Thread.java中的State枚举类
1 /** 2 * A thread state. A thread can be in one of the following states: 3 * <ul> 4 * <li>{@link #NEW}<br> 5 * A thread that has not yet started is in this state. 6 * </li> 7 * <li>{@link #RUNNABLE}<br> 8 * A thread executing in the Java virtual machine is in this state. 9 * </li> 10 * <li>{@link #BLOCKED}<br> 11 * A thread that is blocked waiting for a monitor lock 12 * is in this state. 13 * </li> 14 * <li>{@link #WAITING}<br> 15 * A thread that is waiting indefinitely for another thread to 16 * perform a particular action is in this state. 17 * </li> 18 * <li>{@link #TIMED_WAITING}<br> 19 * A thread that is waiting for another thread to perform an action 20 * for up to a specified waiting time is in this state. 21 * </li> 22 * <li>{@link #TERMINATED}<br> 23 * A thread that has exited is in this state. 24 * </li> 25 * </ul> 26 * 27 * <p> 28 * A thread can be in only one state at a given point in time. 29 * These states are virtual machine states which do not reflect 30 * any operating system thread states. 31 * 32 * @since 1.5 33 * @see #getState 34 */ 35 public enum State { 36 /** 37 * Thread state for a thread which has not yet started. 38 */ 39 NEW, 40 41 /** 42 * Thread state for a runnable thread. A thread in the runnable 43 * state is executing in the Java virtual machine but it may 44 * be waiting for other resources from the operating system 45 * such as processor. 46 */ 47 RUNNABLE, 48 49 /** 50 * Thread state for a thread blocked waiting for a monitor lock. 51 * A thread in the blocked state is waiting for a monitor lock 52 * to enter a synchronized block/method or 53 * reenter a synchronized block/method after calling 54 * {@link Object#wait() Object.wait}. 55 */ 56 BLOCKED, 57 58 /** 59 * Thread state for a waiting thread. 60 * A thread is in the waiting state due to calling one of the 61 * following methods: 62 * <ul> 63 * <li>{@link Object#wait() Object.wait} with no timeout</li> 64 * <li>{@link #join() Thread.join} with no timeout</li> 65 * <li>{@link LockSupport#park() LockSupport.park}</li> 66 * </ul> 67 * 68 * <p>A thread in the waiting state is waiting for another thread to 69 * perform a particular action. 70 * 71 * For example, a thread that has called <tt>Object.wait()</tt> 72 * on an object is waiting for another thread to call 73 * <tt>Object.notify()</tt> or <tt>Object.notifyAll()</tt> on 74 * that object. A thread that has called <tt>Thread.join()</tt> 75 * is waiting for a specified thread to terminate. 76 */ 77 WAITING, 78 79 /** 80 * Thread state for a waiting thread with a specified waiting time. 81 * A thread is in the timed waiting state due to calling one of 82 * the following methods with a specified positive waiting time: 83 * <ul> 84 * <li>{@link #sleep Thread.sleep}</li> 85 * <li>{@link Object#wait(long) Object.wait} with timeout</li> 86 * <li>{@link #join(long) Thread.join} with timeout</li> 87 * <li>{@link LockSupport#parkNanos LockSupport.parkNanos}</li> 88 * <li>{@link LockSupport#parkUntil LockSupport.parkUntil}</li> 89 * </ul> 90 */ 91 TIMED_WAITING, 92 93 /** 94 * Thread state for a terminated thread. 95 * The thread has completed execution. 96 */ 97 TERMINATED; 98 }
线程状态切换图
Note：
阻塞状态是线程因为某种原因放弃CPU使用权，暂时停止运行。直到线程进入就绪状态，才有机会转到运行状态。阻塞的情况分三种：
- 等待阻塞：运行的线程执行wait()方法，JVM会把该线程放入等待池中。(wait会释放持有的锁)
- 同步阻塞：运行的线程在获取对象的同步锁时，若该同步锁被别的线程占用，则JVM会把该线程放入锁池中。
- 其他阻塞：运行的线程执行sleep()或join()方法，或者发出了I/O请求时，JVM会把该线程置为阻塞状态。当sleep()状态超时、join()等待线程终止或者超时、或者I/O处理完毕时，线程重新转入就绪状态。