Java多线程编程初学者：Windows和Mac之间的调度差异 背景

我是一名CS学生，今天在课堂上我们学习了Java多线程编程。教授要求学生编写一个简单的程序来演示线程的调度。每个学生都有这样一段代码：

public class MyThread extends Thread {

    private int num;

    public MyThread(int num) {
        this.num = num;
    }

    public void run() {
        System.out.println("Thread " + num + " is starting.");
    }

    public static void main( String [] args ) {
        for (int i=0; i<100; i++) {
            MyThread mt = new MyThread(i);
            mt.start();
        }
    }
}

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为什么Mac和Windows表现不同？这与所使用的调度算法有关吗？如果是这样的话，算法是什么？这会如何影响其他JVM多线程程序？

在Windows上而不是Mac上排序的数字与操作系统中的调度程序有关。从开发人员的角度来看，您不应该依赖于序列为真，即使在Windows上看起来是这样。在不同的负载或不同的体系结构（处理器上的内核/线程数量、使用的jvm）下，无法保证序列是正确的

为什么Mac和Windows表现不同

线程调度基于操作系统的内部结构。你所能说的就是MacOSX和Windows由于是不同的操作系统而表现不同。如果你有不同的硬件，这也会有不同

这与所使用的调度算法有关吗

创建一个线程非常昂贵，而且您的任务非常短暂，因此在这种情况下，您不太可能看到调度的效果。实际上，您正在测试线程是如何创建的

如果是，算法是什么？这会如何影响其他JVM多线程程序

您需要查看操作系统的内部结构

对编写良好的JVM程序的影响应该是零。您应该编写对特定操作系统或硬件操作方式的细微差异不敏感的程序

你也不应该疯狂地创建线程，这显然是低效的。猜测一个写得不好或效率低下的程序是如何运行的并不是很有用

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我建议从一个多线程比一个线程性能更好的问题开始（在您的示例中，一个线程会更有效），看看调度是否对一系列CPU类型有影响。

尝试将输出重定向到文件或在IDE外部/内部运行。有趣的是，当我在Eclipse和命令行中运行时，行为是相似的（前10个是随机的，然后是严格的升序）。下次我有机会的话，我会尝试在Windows上做。

Thread 0 is starting.
Thread 3 is starting.
Thread 2 is starting.
Thread 1 is starting.
Thread 5 is starting.
Thread 6 is starting.
Thread 4 is starting.
Thread 8 is starting.
Thread 7 is starting.
Thread 9 is starting.
Thread 10 is starting.
Thread 11 is starting.
Thread 12 is starting.
Thread 13 is starting.
Thread 14 is starting.
Thread 15 is starting.
Thread 16 is starting.
Thread 17 is starting.
Thread 18 is starting.
Thread 19 is starting.
Thread 20 is starting.
Thread 21 is starting.
Thread 22 is starting.
Thread 23 is starting.
Thread 24 is starting.
Thread 25 is starting.
Thread 26 is starting.
Thread 27 is starting.
Thread 28 is starting.
Thread 29 is starting.
Thread 30 is starting.
Thread 31 is starting.
Thread 32 is starting.
Thread 33 is starting.
Thread 34 is starting.
Thread 35 is starting.
Thread 36 is starting.
Thread 37 is starting.
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Thread 40 is starting.
Thread 41 is starting.
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