java - 我将我的线程设置为比其他线程更高的优先级，但 CPU 时间似乎是随机的？

Question

我将我的线程设置为比其他线程更高的优先级，但 CPU 时间似乎是随机的？下面是我的程序。

public class Main {

    public static void main(String[] args){

        Priority high=new Priority("High Priority");
        Priority low=new Priority("Low Priority");
        //set the priorities 
        high.thread.setPriority(Thread.NORM_PRIORITY + 2);
        low.thread.setPriority(Thread.NORM_PRIORITY - 2);
        //start the threads
        high.thread.start();
        low.thread.start(); 
        try {
            high.thread.join();
            low.thread.join();
        } catch(Exception e){
            e.printStackTrace();
        }
        System.out.println("\nHigh Priority thread counted to"+high.count);
        System.out.println("\nLow Priority thread counted to"+low.count);
    }
}

我的线程类

public class Priority implements Runnable {
    int count;
    Thread thread;
    static boolean stop = false;
    static String currentName;

    public Priority(String name){
        thread = new Thread(this,name);
        count = 0;
        //Only one version of currentName as it is static
        currentName = name;
    }

    //Begin the execution of the thread
    @Override
    public void run() {
        System.out.println(thread.getName() + " Starting");
        do {
            //enter the thread increment the counter
            count++;
            if (currentName.compareTo(thread.getName()) != 0) {
                currentName=thread.getName();
                System.out.println("In " + currentName);
            }
        } while(stop == false && count < 10000000);
        stop=true;
        System.out.println("\n" + thread.getName() + " terminating.");
    }
}

程序的输出各不相同有时我会得到

High Priority thread counted to10000000

Low Priority thread counted to6266009

其他时候我会得到

High Priority thread counted to4859068

Low Priority thread counted to10000000

Answer 1

在程序的大部分生命周期中，只有两个可运行的线程。如果您在具有两个或更多 CPU 的计算机上运行，​​那么这两个线程的优先级不会有任何区别。仅当要运行的线程多于可供它们运行的​​ CPU 时，优先级才重要。