Java多线程之join方法

概述

可以将两个交替执行的线程合并为顺序执行。比如在线程B中调用了线程A的Join()方法，直到线程A执行完毕后，才会继续执行线程B。(此处为常见面试考点)

join()让线程之间的执行变为了串行.

demo

FirstThread:

public class FirstThread extends Thread {
    
    

	public FirstThread(String name) {
    
    
		super(name);
	}

	@Override
	public void run() {
    
    
		for (int i = 0; i <= 20; i++) {
    
    
			System.out.println(this.getName() + ":" + i);
		}
	}
}

SecondThread

public class SecondThread extends Thread {
    
    
	public SecondThread(String name) {
    
    
		super(name);
	}

	@Override
	public void run() {
    
    
		for (int i = 0; i <= 20; i++) {
    
    
			System.out.println(this.getName() + ":" + i);
		}
	}
}

TestThread

public class TestThread {
    
    

	public static void main(String[] args) throws InterruptedException {
    
    

		FirstThread firstThread = new FirstThread("第一个线程");
		SecondThread secondThread = new SecondThread("第二个线程");
		firstThread.start();
		/*
		 不加join()方法, 两个线程会交替执行
		 *firstThread线程加了join()之后 firstThread 线程会优先全部执行完secondThread线程才会执行
		 join()让线程之间的执行变为了串行.
		 * */
		firstThread.join();
		secondThread.start();


	}

}