如何控制线程执行的先后顺序

1.如果你有三个线程，分别为T1,T2,T3,如何让线程T2在线程T1之后执行，在线程T3之前执行。

答案是：使用线程的join方法，该方法的作用是“等待线程执行结束”，即join()方法后面的代码块都要等待现场执行结束后才能执行。事例代码如下：

Java代码  package com.liuan.job;  

public class Test {
    @SuppressWarnings("static-access")
    public static void main(String[] args) throws InterruptedException {
        Thread t1 = new Thread(new Runner());
        Thread t2 = new Thread(new Runner());
        Thread t3 = new Thread(new Runner());
        t1.start();
        t1.sleep(5000);
        t1.join();

        t2.start();
        t2.sleep(1000);
        t2.join();
        t3.start();
        t3.join();

    }

}

class Runner implements Runnable{

    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName()+"");

    }

}

package com.liuan.job;

public class Test {
	@SuppressWarnings("static-access")
	public static void main(String[] args) throws InterruptedException {
		Thread t1 = new Thread(new Runner());
		Thread t2 = new Thread(new Runner());
		Thread t3 = new Thread(new Runner());
		t1.start();
		t1.sleep(5000);
		t1.join();
	
		t2.start();
		t2.sleep(1000);
		t2.join();
		t3.start();
		t3.join();
	
	}
	
}

class Runner implements Runnable{

	@Override
	public void run() {
		System.out.println(Thread.currentThread().getName()+"");
		
	}
	
}

 执行结果是：

 

Thread-0
Thread-1
Thread-2

 

2.补充

线程的优先级无法保障线程的执行次序。只不过优先级高的线程获取 CPU 资源的概率大一点而已。