Java Thread Join

最新推荐文章于 2025-06-22 12:23:47 发布

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本文通过实例详细介绍了Java中Thread类的join方法的使用方法及其三个重载版本。通过join方法，主线程可以等待子线程执行完毕后再继续执行，这对于实现线程间的同步非常重要。

1. Java Thread join 用来使当前线程 pause 等待调用该方法的线程 dead ；java 有三个join 方法：

public final void join()

public final synchronized void join(long millis)

public final synchronized void join(long millis, int nanos)

public class ThreadJoinExample {
 
    public static void main(String[] args) {
        Thread t1 = new Thread(new MyRunnable(), "t1");
        Thread t2 = new Thread(new MyRunnable(), "t2");
        Thread t3 = new Thread(new MyRunnable(), "t3");
         
        t1.start();
         
        //start second thread after waiting for 2 seconds or if it's dead
        try {
            t1.join(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
         
        t2.start();
         
        //start third thread only when first thread is dead
        try {
            t1.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
         
        t3.start();
         
        //let all threads finish execution before finishing main thread
        try {
            t1.join();
            t2.join();
            t3.join();
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
         
        System.out.println("All threads are dead, exiting main thread");
    }
 
}
 
class MyRunnable implements Runnable{
 
    @Override
    public void run() {
        System.out.println("Thread started:::"+Thread.currentThread().getName());
        try {
            Thread.sleep(4000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("Thread ended:::"+Thread.currentThread().getName());
    }
     
}