Java中线程基础-线程间协作-join()方法

join()方法

面试点

线程A，执行了线程B(对象)的join()方法，线程A必须要等待B执行完成了以后，线程A才能继续自己的工作。 

 线程休眠辅助工具类

package com.xiangxue.tools;

import java.util.concurrent.TimeUnit;

/**
 * 
 *
 *类说明：线程休眠辅助工具类
 */
public class SleepTools {
	
	/**
	 * 按秒休眠
	 * @param seconds 秒数
	 */
    public static final void second(int seconds) {
        try {
            TimeUnit.SECONDS.sleep(seconds);
        } catch (InterruptedException e) {
        }
    }
    
    /**
     * 按毫秒数休眠
     * @param seconds 毫秒数
     */
    public static final void ms(int seconds) {
        try {
            TimeUnit.MILLISECONDS.sleep(seconds);
        } catch (InterruptedException e) {
        }
    }
}

演示下join方法的使用

package com.xiangxue.ch1;

import com.xiangxue.tools.SleepTools;
/**
 *
 *
 *类说明：演示下join方法的使用
 */
public class UseJoin {
	
	//内部类
    static class JumpQueue implements Runnable {
        private Thread thread;//用来插队的线程

        public JumpQueue(Thread thread) {
            this.thread = thread;
        }
        
        @Override //覆写
        public void run() {
        	try {
        		System.out.println(thread.getName()+" will be join before "
        				+Thread.currentThread().getName());
				thread.join();
			} catch (InterruptedException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
        	System.out.println(Thread.currentThread().getName()+" terminted.");
        }
    }

    public static void main(String[] args) throws Exception {
        Thread previous = Thread.currentThread();//现在是主线程
        for (int i = 0; i < 10; i++) {
            //i=0,previous 是主线程，i=1;previous是i=0这个线程
            Thread thread =
                    new Thread(new JumpQueue(previous), String.valueOf(i));
            System.out.println(previous.getName()+" jump a queue the thread:"
                    +thread.getName());
            thread.start();
            previous = thread;
        }

        SleepTools.second(6);//让主线程休眠6秒
        System.out.println(Thread.currentThread().getName() + " terminate.");
    }
}

控制台打印输出