Question

后面的代码给出了我无法理解的输出。

我有2个整数：计数和锁定。如果我同步“锁定”（如代码中所示），则输出显示“count”按预期添加，但“锁定”添加错误。
为什么会这样？如果我同步它，我无法改变“锁定”吗？

以下是代码：

public class SynchronizedTest implements Runnable {

    static Integer count = new Integer(0);
    static Integer lock = new Integer(0);
    private int threadIndex = -1;

    public SynchronizedTest(int threadIndex) {
        this.threadIndex = threadIndex;
    }

    @Override
    public void run() {
        System.out.println("in");
        for (int i = 0; i < 10; ++i) {
            try {
                Thread.sleep(50);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            synchronized (SynchronizedTest.lock) {
                count++;
                lock++;
                System.out.println("Thread " + threadIndex + ": " + count);
                System.out.println("Thread " + threadIndex + " lock : " + lock);
            }
        }
        System.out.println("out");
    }

    public static void main(String[] args) {
        for (int i = 0; i < 5; ++i) {
            SynchronizedTest threadTest = new SynchronizedTest(i);
            Thread thread = new Thread(threadTest);
            thread.start();
        }
    }
}

输出结果为：

in  
in  
in  
in  
in  
Thread 4: 1  
Thread 4 lock : 1  
Thread 0: 2  
Thread 0 lock : 2  
Thread 1: 3  
Thread 3: 4  
Thread 1 lock : 4  
Thread 3 lock : 4  
Thread 2: 5  
Thread 2 lock : 5  
Thread 1: 6  
Thread 1 lock : 6  
Thread 3: 7  
Thread 3 lock : 7  
Thread 4: 8  
Thread 2: 10  
Thread 0: 9  
Thread 2 lock : 10  
Thread 4 lock : 10  
Thread 0 lock : 10  
Thread 1: 11  
Thread 0: 14  
Thread 0 lock : 14  
Thread 2: 13  
Thread 2 lock : 14  
Thread 3: 12  
Thread 3 lock : 14  
Thread 1 lock : 14  
Thread 4: 15  
Thread 4 lock : 15  
Thread 0: 16  
Thread 0 lock : 16  
Thread 2: 17  
Thread 1: 19  
Thread 1 lock : 19  
Thread 3: 18  
Thread 3 lock : 19  
Thread 2 lock : 19  
Thread 4: 20  
Thread 4 lock : 20  
Thread 1: 21  
Thread 1 lock : 21  
Thread 2: 22  
Thread 0: 23  
Thread 2 lock : 23  
Thread 0 lock : 23  
Thread 3: 24  
Thread 3 lock : 24  
Thread 4: 25  
Thread 4 lock : 25  
Thread 1: 26  
Thread 1 lock : 26  
Thread 2: 27  
Thread 3: 29  
Thread 0: 28  
Thread 3 lock : 29  
Thread 2 lock : 29  
Thread 0 lock : 29  
Thread 4: 30  
Thread 4 lock : 30  
Thread 1: 31  
Thread 1 lock : 31  
Thread 3: 32  
Thread 0: 33  
Thread 3 lock : 33  
Thread 0 lock : 33  
Thread 2: 34  
Thread 2 lock : 34  
Thread 4: 35  
Thread 4 lock : 35  
Thread 1: 36  
Thread 1 lock : 36  
Thread 3: 37  
Thread 3 lock : 37  
Thread 2: 39  
Thread 0: 39  
Thread 2 lock : 39  
Thread 0 lock : 39  
Thread 4: 40  
Thread 4 lock : 40  
Thread 1: 41  
Thread 1 lock : 41  
Thread 3: 42  
Thread 0: 43  
Thread 3 lock : 43  
Thread 0 lock : 43  
Thread 2: 44  
Thread 2 lock : 44  
Thread 4: 45  
Thread 4 lock : 45  
Thread 1: 47  
Thread 2: 49  
Thread 2 lock : 49  
Thread 0: 48  
Thread 3: 47  
Thread 3 lock : 49  
out  
Thread 0 lock : 49  
out  
out  
Thread 1 lock : 49  
out  
Thread 4: 50  
Thread 4 lock : 50  
out

Answer 1

您没有使用相同的锁，因为您正在更改整数，每次增加锁时都会创建一个新对象，只需使用一个新对象而不要更改。

具有意外输出的同步代码

1 个答案: