join()

主要作用是同步，它可以使得线程之间的并行执行变为串行执行。在A线程中调用了B线程的join()方法时，表示只有当B线程
执行完毕时，A线程才能继续执行。

 

/**
 * join方法的使用
 */
public class UseJoin {
    private static class JumpQueue implements Runnable {
        private Thread thread;  // 用来插队的线程
        public JumpQueue(Thread thread) {
            this.thread = thread;
        }

        public void run() {
            try {
                thread.join();
                System.out.println(Thread.currentThread().getName()+" is running!");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) throws Exception {
        Thread previous = Thread.currentThread();//现在是主线程
        for (int i = 0; i < 3; i++) {
            Thread thread = new Thread(new JumpQueue(previous), "线程" + i);
            System.out.println(previous.getName() + " inserts in front of " + thread.getName());
            thread.start();
            previous = thread;
        }
        System.out.println(Thread.currentThread().getName() + " end!");
    }
}