线程优先级，守护线程

1、线程优先级

　　Thread源码优先级定义1-10

    /**
     * The minimum priority that a thread can have.
     */
    public final static int MIN_PRIORITY = 1;

   /**
     * The default priority that is assigned to a thread.
     */
    public final static int NORM_PRIORITY = 5;

    /**
     * The maximum priority that a thread can have.
     */
    public final static int MAX_PRIORITY = 10;

　　

　　调度器倾向于让优先级高的先执行，但是CPU处理线程的顺序是不确定的。优先级低的线程只是执行的频率较低。一般线程已默认优先级运行，试图操作优先级是一种错误

 

2、daemon（守护线程，后台线程）

　　程序在运行时在后台提供一种服务的线程。所有非守护线程结束时，程序终止，守护线程也终止。

/**
 * 守护线程测试类
 * @author monkjavaer
 * @date 2018/11/22 22:54
 */
public class DaemonsThread implements Runnable {

    @Override
    public void run() {
        try {
            while (true) {
                TimeUnit.MILLISECONDS.sleep(100);
                System.out.println("守护线程"+Thread.currentThread() + " " + this);
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) throws InterruptedException {
        for (int i=0;i<10;i++) {
            Thread thread = new Thread(new DaemonsThread());
            thread.setDaemon(true);
            thread.start();
        }
        System.out.println("main线程执行完===");
        TimeUnit.MILLISECONDS.sleep(1000);
    }
}