Java线程状态

Posted 2021-12-14 小志的博客

目录

• • 1、Java线程6中状态
  • 2、Tread类中State枚举定义的6种状态
  • 3、各种状态的图解
  • 4、各种状态的解释

1、Java线程6中状态

Java线程一共分为6种状态，如下所示

• NEW：新建状态
• RUNNABLE：就绪状态
• BLOCKED：阻塞状态
• WAITING：等待状态
• TIMED_WAITING：限时等待状态
• TERMINATED：结束状态

2、Tread类中State枚举定义的6种状态

通过Tread中的State枚举查看这六种状态的定义，如下所示：

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;
    

3、各种状态的图解

各种状态图解，如下图所示：

4、各种状态的解释

• NEW状态
  表示刚刚创建的线程，这种线程还没开始执行。等到线程的start()方法调用时，才表示线程开始执行。

• RUNNABLE状态
  表示线程所需的一切资源都已经准备好了。处于就绪状态的线程，只是说明此线程已经做好了被运行的准备，随时等待CPU调度执行，而并不是说调用了start()方法，这个线程就会被立即运行。

• BLOCKED状态
  如果线程在执行过程中遇到了synchronized或者Lock，那么就会进入到阻塞状态。处于阻塞状态的线程会放弃对CPU的使用权，停止执行，直到次线程进入到了就绪的状态，才会有机会再次被CPU调用运行。

• WAITING状态
  如果线程被调用了没有超时时间的wait方法，那么会进入无限等待状态。直到被notify通知才可以继续执行。

• TIMED_WAITING状态
  与WAITING状态相似，区别是，在有限的时间内进行线程等待。