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();


  }

}