深入理解join()方法

全文概要

本文主要介绍Thread中join()方法的使用场景。

join()方法介绍

• 代码案例

package com.tml.javaCore.thread;

/**
 * <p>Thread类中join()方法
 * @author Administrator
 *
 */
public class JoinDemo {
	public static void main(String[] args) {
		JoinDemo demo = new JoinDemo();
		Thread thread_01  = new  Thread(new  Runnable() {
			public void run() {
				System.out.println(Thread.currentThread().getName() + "ready！");
				
				
				Thread thread_02 =new Thread(new  Runnable() {
					public void run() {
						System.out.println(Thread.currentThread().getName() + "ready！");
						demo.print();
						System.out.println(Thread.currentThread().getName() + " end！");
					}
				}, "thread_02");
				thread_02.start();
				try {
					thread_02.join();
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
				demo.print();
				System.out.println(Thread.currentThread().getName() + " end！");
				
			}
		}, "thread_01");
		
		thread_01.start();
		
		
	}
	
	
	private void  print(){
		for(int i=0;i<10;i++){
			try {
				Thread.sleep(1000);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			System.out.println(Thread.currentThread().getName() +" :is printing :" + i);
		}
	}

}

• 输出结果
  

    thread_01ready！
    thread_02ready！
    thread_02 :is printing :0
    thread_02 :is printing :1
    thread_02 :is printing :2
    thread_02 :is printing :3
    thread_02 :is printing :4
    thread_02 :is printing :5
    thread_02 :is printing :6
    thread_02 :is printing :7
    thread_02 :is printing :8
    thread_02 :is printing :9
    thread_02 end！
    thread_01 :is printing :0
    thread_01 :is printing :1
    thread_01 :is printing :2
    thread_01 :is printing :3
    thread_01 :is printing :4
    thread_01 :is printing :5
    thread_01 :is printing :6
    thread_01 :is printing :7
    thread_01 :is printing :8
    thread_01 :is printing :9

    thread_01 end！

• 结果分析

1. 在main主线程中启动一个线程thread_01，而线程1中又新建了一个线程thread_02，执行thread_02.start()时启动了线程2；
2. 当执行到thread_02.join()时，会让线程1进入阻塞等待状态，直到线程2全部执行完毕后，线程1才能执行；
3. join()方法的使用场景也就不言而喻了，即主线程等待子线程全部执行完毕后，才继续执行主线程后续的逻辑。