Java线程join()
方法可用于暂停当前线程执行,除非指定的线程已死亡。有三个重载的join()
方法。
public final void join()
:这个java线程join()
方法使当前线程处于等待状态,直到调用它的线程死亡。如果线程被中断,则抛出InterruptedException
异常。public final synchronized void join(long millis)
: 这个java线程join()
方法用于等待它被调用的线程死或等待指定的毫秒。由于线程执行依赖于OS实现,因此不保证当前线程只等待给定时间。public final synchronized void join(long millis, int nanos)
:这个java线程join()
方法用于等待线程死亡给定的毫秒加纳秒。
下面是一个显示Thread
的join()
方法用法的简单示例。该程序的目标是确保main
是最后一个完成的线程,第三个线程只在第一个线程死亡时启动。
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());
}
}
执行上面程序,得到以下结果 -
Thread started:::t1
Thread started:::t2
Thread ended:::t1
Thread started:::t3
Thread ended:::t2
Thread ended:::t3
All threads are dead, exiting main thread