线程的优先级(读书笔记)

     Java中的线程可以有自己的优先级,优先级高的线程在竞争资源时会更有优势,更可能抢占资源.

     Java中 使用1到10表示线程优先级,一般可以使用内置的三个静态变量表示:

 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;

 

     数字越大则优先级越高,但有效范围在1到10之间, 高优先级的线程倾向于更快的完成工作.

public class PriorityDemo {
    public static class HightProprity extends Thread {
        static int count = 0;

        public void run() {
            while (true) {
                synchronized (PriorityDemo.class) {
                    count++;
                    if (count > 10000000) {
                        System.out.println("HightPriority is complete");
                        break;
                    }
                }
            }
        }
    }

    public static class LowPriority extends Thread {
        static int count = 0;

        public void run() {
            while (true) {
                synchronized (PriorityDemo.class) {
                    count++;
                    if (count > 10000000) {
                        System.out.println("LowPriority is complete");
                        break;
                    }
                }
            }
        }
    }

    public static void main(String[] args) {
        Thread high = new HightProprity();
        Thread low = new LowPriority();
        high.setPriority(Thread.MAX_PRIORITY);
        low.setPriority(Thread.MIN_PRIORITY);
        low.start();
        high.start();
    }
}

我们尝试执行上述代码,可以看到 大部分情况下.高优先级的线程大部分情况下,就会首先完成任务.