多线程16-多线程的优先级

线程的优先级

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来决定应该调度哪个线程来执行

线程的优先级用数字来表示，范围从1-10

• Thread.MIN_PRIORITY = 1;
• Thread.MAX_PRIORITY = 10;
• Thread.NORM_PRIORITY = 5;

使用以下方法来改变或获取优先级

getPriority(); setPriority(int xx);

t5.setPriority(-1);
        t5.start();

        t6.setPriority(11);
        t6.start();

输出：Exception in thread "main" java.lang.IllegalArgumentException
	at java.lang.Thread.setPriority(Thread.java:1089)
	at com.faq.priority.TestPriority.main(TestPriority.java:30)
超出上下限报错

package com.faq.priority;

//测试线程的优先级
public class TestPriority {
    public static void main(String[] args) {

        //主线程默认优先级
        System.out.println(Thread.currentThread().getName()+"-->"+Thread.currentThread().getPriority());

        MyPriorit myPriorit = new MyPriorit();
        Thread t1 = new Thread(myPriorit);
        Thread t2 = new Thread(myPriorit);
        Thread t3 = new Thread(myPriorit);
        Thread t4 = new Thread(myPriorit);
       

        //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();


    }

}

class MyPriorit implements Runnable{
    public void run(){
        System.out.println(Thread.currentThread().getName()+"-->"+Thread.currentThread().getPriority());
    }
}
输出：main-->5
Thread-3-->10
Thread-0-->5
Thread-2-->4
Thread-1-->1

优先级低只是意味着被调度的概率低，而不是不会被调用，这要看cpu的调度