线程优先级

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
• 线程的优先级用数字表示，范围从1~10.
  • Thread.MIN_PRIORITY = 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)
• 线程优先级最大设置为10，最小为1，不在这个范围内的都会报出异常
• 每一个程序都是主线程先执行，后执行子线程，默认线程优先级为5

优先级的设定建议在start之前进行设置

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，也有可能低优先级的线程先调度

public class TestPriority {
    public static void main(String[] args) {
        //主线程的默认优先级
        System.out.println(Thread.currentThread().getName()+"-->"+Thread.currentThread().getPriority());
        MyPriority myPriority = new MyPriority();
        Thread thread = new Thread(myPriority);
        Thread thread1 = new Thread(myPriority);
        Thread thread2 = new Thread(myPriority);
        Thread thread3 = new Thread(myPriority);
        Thread thread4 = new Thread(myPriority);

        //先设置优先级,再启动
        thread.start();
        thread1.setPriority(1);
        thread1.start();
        thread2.setPriority(4);
        thread2.start();
        thread3.setPriority(Thread.MAX_PRIORITY);
        thread3.start();
        thread4.setPriority(6);
        thread4.start();
    }

}

class MyPriority implements Runnable{

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