Question

我在Java中编写了一个多线程程序，如下所示： -

public class Client {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub


        Counter counter = new Counter();

        int val = counter.getValue();
        while(val < 5){
            val = counter.getValue();
            System.out.println("In main thread : "+val);
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
    }

}
}

class Counter implements Runnable {

    private int countValue;
    Counter(){
        countValue = 0;
        Thread thread = new Thread(this ,"Counter A");
        Thread thread1 = new Thread(this    ,"Counter B");
        thread.start();
        thread1.start();
    }

    int getValue(){
        return countValue;
    }

    @Override
    public void run() {
        // TODO Auto-generated method stub
        while( countValue < 5){

                System.out.println("In child thread : "+ ++countValue );
                try {
                    Thread.sleep(250);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
    }

}
}

程序的输出是输出： -

In main thread : 0  
In child thread : 2   
In child thread : 1   
In child thread : 3  
In child thread : 3  
In child thread : 4  
In child thread : 5  
In main thread : 5

有人能详细解释一下这个输出是怎么来的。谢谢你提前

Answer 1

你有3个线程（主线程和2个子线程）并行运行（除非你有一个proc盒子），它们都在读取和写入一个不受任何保护的资源countValue同步。

当你做这样的事情时，你会得到明显的随机输出。

Java中的多线程产生了2个线程

1 个答案: