线程优先级

Java提供一个线程调度器来监控程序中启动后进入就绪状态的所有线程，线程调度器按照优先级决定应该调度哪个线程来执行。

image-20210310151353768

线程的优先级用数字表示,范围从1~10

• Thread. MIN_PRIORTY=1
• Thread. MAX_PRIORITY= 10
• Thread. NORM_PRIORITY= 5

使用以下方式改变或获取优先级

• getPriority(). setPriority(int xxx)

image-20210310151553469

先设置优先级，再启动线程。

public class TestPriority{
    public static void main(String[] args) {
        // 主线程默认优先级,无法修改
        System.out.println(Thread.currentThread().getName()+"===>" + Thread.currentThread().getPriority());

        MyPriority myPriority = new MyPriority();
        Thread t1 = new Thread(myPriority);
        Thread t2 = new Thread(myPriority);
        Thread t3 = new Thread(myPriority);
        Thread t4 = new Thread(myPriority);
        Thread t5 = new Thread(myPriority);
        Thread t6 = new Thread(myPriority);

        // 先设置优先级,再启动
        t1.start();

        t2.setPriority(1);
        t2.start();

        t3.setPriority(4);
        t3.start();

        t4.setPriority(Thread.MAX_PRIORITY);
        t4.start();

        t5.setPriority(8);
        t5.start();

        t6.setPriority(7);
        t6.start();
    }
}

class MyPriority implements Runnable{
    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName()+"===>" + Thread.currentThread().getPriority());
    }
}

优先级低只是意味着获得调度的概率低。并不是优先级低就不会被调用了。这都是看CPU的调度。