java线程的6种状态以及相互转换

线程如何创建

创建线程有三种方式：继承Thread类；无返回值的Runnable；有返回值的Callable

示例如下

package com.rcl.platform.demo;import java.util.concurrent.Callable;import java.util.concurrent.ExecutionException;import java.util.concurrent.FutureTask;public class CreateThread { public static class TestThread extends Thread {  @Override  public void run() {   System.out.println("--继承thread--");  } } public static class TestRunnable implements Runnable {  @Override  public void run() {   System.out.println("--runnable没有返回值--");  } } public static class TestCallable implements Callable<String> {  @Override  public String call() throws Exception {   System.out.println("--callable有返回值--");   return "test-callable";  } } public static void main(String[] args) throws InterruptedException, ExecutionException {  Thread thread = new Thread(new TestThread());  thread.start();  thread = new Thread(new TestRunnable());  thread.start();  FutureTask<String> ft = new FutureTask<>(new TestCallable());   thread = new Thread(ft);  thread.start();  System.out.println(ft.get()); }}

执行结果

--继承thread----runnable没有返回值----callable有返回值--test-callable

线程相关的基础方法

wait：获取锁对象monitor的线程执行wait方法，将会释放对monitor的控制权，其他线程可以获取到锁对象的monitor，执行notify唤醒wait线程

notify/notifyall：获取到monitor，唤醒曾经获取到monitor执行wait正在处于等待的线程（线程状态为WAITING，TIMED_WAITING）

sleep：线程休眠

yield：yield方法的作用是暂停当前线程，以便其他线程有机会执行，不过不能指定暂停的时间，并且也不能保证当前线程马上停止。yield方法只是将Running状态转变为Runnable状态（不能完全保证，最好少用）

join：join方法的作用是父线程等待子线程执行完成后再执行，换句话说就是将异步执行的线程合并为同步的线程，如：如果在mian线程执行的过程中执行t1.join方法，那么将转而执行t1线程，t1线程执行完毕后执行mian线程

package com.rcl.platform.demo;import java.util.concurrent.ExecutionException;import java.util.concurrent.TimeUnit;public class JoinTest { public static class TestThread extends Thread {  @Override  public void run() {   for(int i=0; i<10; i++){    System.out.println("第" + i + "次执行");    try {     TimeUnit.SECONDS.sleep(1);    } catch (InterruptedException e) {     e.printStackTrace();    }   }  } } public static void main(String[] args) throws InterruptedException, ExecutionException {  TestThread thread = new TestThread();  thread.start();  thread.join();  System.out.println("等待thread执行完毕后main线程结束"); }}

执行结果

第0次执行第1次执行第2次执行第3次执行第4次执行第5次执行第6次执行第7次执行第8次执行第9次执行等待thread执行完毕后main线程结束

interrupt：他的作用是“停止”当前线程的运行，为什么加上一个引号，它只在特殊情况下有用，像线程调用了wait,sleep,join等可中断的阻塞方法 后，调用interrupt就会抛出InterruptedException异常。其实它称为协作停止。调用了这个方法后线程除了特殊情况外别的时候并不会停止，它发送一个停止请求，并且由线程记录下来（实际上就是有一个为bool的变量，当为true时就表示有停止线程运行请求）。所以说线程真正的停止需要我们自己去检查是否有停止线程的请求，当有线程停止请求时停用当前线程。和他配套是使用的有

public static boolean interrupted()

public boolean isInterrupted()

package com.rcl.platform.demo;import java.util.concurrent.ExecutionException;import java.util.concurrent.TimeUnit;public class JoinTest { public static class TestThread extends Thread {  @Override  public void run() {   for(int i=0; i<1000000000; i++){    System.out.println("TestThread第" + i + "次执行");    if(Thread.interrupted()){      return;     }  }  } } public static class TestThreadSleep extends Thread {  @Override  public void run() {   for(int i=0; i<10; i++){    System.out.println("TestThreadSleep第" + i + "次执行");    try {     TimeUnit.SECONDS.sleep(1);    } catch (InterruptedException e) {     e.printStackTrace();    }    if(Thread.interrupted()){      return;     }  }  } } public static void main(String[] args) throws InterruptedException, ExecutionException {  TestThread thread = new TestThread();  thread.start();  thread.interrupt();  TestThreadSleep threadSleep = new TestThreadSleep();  threadSleep.start();  threadSleep.interrupt(); }}

执行结果

TestThread第0次执行TestThreadSleep第0次执行java.lang.InterruptedException: sleep interruptedTestThreadSleep第1次执行 at java.lang.Thread.sleep(Native Method) at java.lang.Thread.sleep(Thread.java:340) at java.util.concurrent.TimeUnit.sleep(TimeUnit.java:386) at com.rcl.platform.demo.JoinTest$TestThreadSleep.run(JoinTest.java:27)TestThreadSleep第2次执行TestThreadSleep第3次执行TestThreadSleep第4次执行TestThreadSleep第5次执行TestThreadSleep第6次执行TestThreadSleep第7次执行TestThreadSleep第8次执行TestThreadSleep第9次执行

线程状态

1、java线程有6中状态，分别为NEW，RUNNABLE，BLOCKED，WAITING，TIMED_WAITING，TERMINATED详解java.lang.Thread$State枚举类

2、线程初始化为NEW状态，该状态表示还未调用start方法

3、执行线程调用start方法，线程状态转换为RUNNABLE（包括竞争到CPU时间真正意义的执行和没有竞争到CPU时间等待下一个CPU时间的状态）

4、BLOCKED状态为锁竞争，没有竞争到锁为BLOCKED，等待拥有锁的线程释放锁，进入RUNNABLE状态

5、WAITING状态为竞争到锁，执行wait方法，又释放锁，本线程进入WAITING，等待其他线程唤醒notify，notifyall，如果不唤醒，将一直处于WAITING状态

6、TIMED_WAITING为执行sleep join或者有时限的等待

7、线程执行完毕，线程处于TERMINATED状态

线程状态变化

package com.rcl.platform.demo;import java.util.concurrent.TimeUnit;public class ThreadState { public static void main( String[] args ) throws InterruptedException {  System.out.println("-------------NEW-------------");  Thread thread = new Thread();  System.out.println(thread.getState() + ":" + (thread.getState() == Thread.State.NEW));  System.out.println("-------------分割线-------------");  System.out.println("-------------RUNNABLE、TERMINATED-------------");  thread = new Thread(new Runnable() {   public void run() {    System.out.println(Thread.currentThread().getState() + ":" + (Thread.currentThread().getState() == Thread.State.RUNNABLE));   }  });  thread.start();  TimeUnit.SECONDS.sleep(1);  System.out.println(thread.getState() + ":" + (thread.getState() == Thread.State.TERMINATED));  System.out.println("-------------分割线-------------");  System.out.println("-------------RUNNABLE、TIMED_WAITING-------------");  thread = new Thread(new Runnable() {   public void run() {    System.out.println(Thread.currentThread().getState() + ":" + (Thread.currentThread().getState() == Thread.State.RUNNABLE));    System.out.println("sleep 进入 TIMED_WAITING");    try {     TimeUnit.SECONDS.sleep(2);    } catch (InterruptedException e) {     e.printStackTrace();    }   }  });  thread.start();  TimeUnit.SECONDS.sleep(1);  System.out.println(thread.getState() );  TimeUnit.SECONDS.sleep(2);  System.out.println("-------------分割线-------------");  System.out.println("-------------RUNNABLE、TIMED_WAITING-------------");  final Thread mainThread = Thread.currentThread();  thread = new Thread(new Runnable() {   public void run() {    System.out.println(Thread.currentThread().getState() + ":" + (Thread.currentThread().getState() == Thread.State.RUNNABLE));    try {     System.out.println("join 进入 TIMED_WAITING");     System.out.println("mainThread: " + mainThread.getState());     TimeUnit.SECONDS.timedJoin(mainThread, 2);//先执行mainthread      System.out.println("mainThread: " + mainThread.getState());    } catch (InterruptedException e) {     e.printStackTrace();    }   }  });  thread.start();  TimeUnit.SECONDS.sleep(1);  System.out.println("testThread: " + thread.getState() );  System.out.println("-------------分割线-------------");  System.out.println("-------------RUNNABLE、WAITING-------------");  Object lock = new Object();  final Thread mainThread1 = Thread.currentThread();  thread = new Thread(new Runnable() {   public void run() {    synchronized (lock) {     try {      System.out.println("wait 进入 WAITING");      lock.wait();      System.out.println("mainThread1: " + mainThread1.getState() );     } catch (InterruptedException e) {      e.printStackTrace();     }    }   }  });  thread.start();  TimeUnit.SECONDS.sleep(1);  System.out.println("testThread: " + thread.getState() );  synchronized (lock) {   lock.notifyAll();  }  TimeUnit.SECONDS.sleep(1);  System.out.println("-------------分割线-------------");  Thread thread1 = new Thread(new Runnable() {   public void run() {    synchronized (lock) {     try {      TimeUnit.SECONDS.sleep(2);     } catch (InterruptedException e) {      e.printStackTrace();     }    }   }  });  thread1.start();  Thread thread2 = new Thread(new Runnable() {   public void run() {    synchronized (lock) {    }   }  });  thread2.start();  TimeUnit.SECONDS.sleep(1);  System.out.println("thread2: " + thread2.getState() ); }}

执行结果

-------------NEW-------------NEW:true-------------分割线--------------------------RUNNABLE、TERMINATED-------------RUNNABLE:trueTERMINATED:true-------------分割线--------------------------RUNNABLE、TIMED_WAITING-------------RUNNABLE:truesleep 进入 TIMED_WAITINGTIMED_WAITING-------------分割线--------------------------RUNNABLE、TIMED_WAITING-------------RUNNABLE:truejoin 进入 TIMED_WAITINGmainThread: TIMED_WAITINGtestThread: TIMED_WAITING-------------分割线--------------------------RUNNABLE、WAITING-------------wait 进入 WAITINGmainThread: TIMED_WAITINGtestThread: WAITINGmainThread1: TIMED_WAITING-------------分割线-------------thread2: BLOCKED

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原标题：java线程的6种状态以及相互转换

关键词：JAVA