在两个线程和主程序之间共享对象 [英] Sharing an object between two threads and main program

问题描述

我是Java的新手，我正在参加并发编程课程。我拼命地试图获得一个最小的工作示例，可以帮助演示概念，我学到了像使用'synchronized'关键字和跨线程共享对象。
一直在搜索，但不能得到一个基本框架。 Java程序员，亲切的帮助。

I am new to Java and I'm attending a Concurrent Programming course. I am desperately trying to get a minimal working example that can help to demonstrate concepts I have learnt like using 'synchronized' keyword and sharing an object across threads. Have been searching, but could not get a basic framework. Java programmers, kindly help.

推荐答案

这里是一个非常好的例子在两个线程之间共享数组。通常你会看到所有的零，但有时会出现螺旋，你看到其他数字。

Here is a very shot example of sharing an array between two threads. Usually you will see all zeros, but sometimes things get screwy and you see other numbers.

final int[] arr = new int[100];
Thread one = new Thread() {
    public void run() {
        // synchronized (arr) {
            for (int i = 0; i < arr.length * 100000; i++) {
                arr[i % arr.length]--;
            }
        // }
    }
};
Thread two = new Thread() {
    public void run() {
        // synchronized (arr) {
            for (int i = 0; i < arr.length * 100000; i++) {
                arr[i % arr.length]++;
            }
        //}
    }
};
one.start();
two.start();
one.join();
two.join();
for (int i = 0; i < arr.length; i++) {
    System.out.println(arr[i]);
}

$ b < c $ c>在循环周围，你将总是看到打印输出中的所有 0 。如果取消注释同步块，代码将运行没有错误。

But, if you synchronize on arr around the looping you will always see all 0s in the print out. If you uncomment the synchronized block, the code will run without error.

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