使用synchronized关键字封装一个锁

代码如下：

1public class Lock {
2    private boolean isLocked = false;
3
4    public void lock() {
5        synchronized (this) {
6            while (isLocked) {
7                try {
8                    wait();
9                } catch (InterruptedException e) {
10                    e.printStackTrace();
11                    isLocked = false;
12                    break;
13                }
14            }
15            isLocked = true;
16        }
17    }
18
19
20    public void unLock() {//也可以把synchronized放在方法前
21        synchronized (this) {
22            isLocked = false;
23            notifyAll();
24        }
25    }
26}

用法如下：

1public class Counter {
2    private int count = 0;
3
4    private Lock mLock = new Lock();
5
6    public void inc(){
7        mLock.lock();
8        count++;
9        mLock.unLock();
10    }
11
12    public int getCount(){
13        return count;
14    }
15
16    public static void main(String[] args) throws InterruptedException {
17
18        Counter counter = new Counter();
19
20        for (int i = 0; i < 500; i++) {
21            new Thread(new Runnable() {
22                @Override
23                public void run() {
24
25                    try {
26                        Thread.currentThread().sleep(100);
27                    } catch (InterruptedException e) {
28                        e.printStackTrace();
29                    }
30                    counter.inc();
31                }
32            }).start();
33        }
34
35
36        Thread.currentThread().sleep(1000 * 5);
37        System.out.println("count=" + counter.getCount());
38    }
39}
40

打印的结果如下：