利用CAS构造一个TryLock自定义显式锁

CAS的全称是Compare And Swap 即比较交换

CAS的博文

TryLock实现类CompareAndSetLock.java

public class CompareAndSetLock {

    private AtomicInteger value = new AtomicInteger(0);
    private Thread threadLocal;

    /**
     * 
get lock
     */
    public void tryLock() throws GetTryLockException {
        boolean success = value.compareAndSet(0, 1);
        if(!success){
            throw new GetTryLockException("get lock fail");
        }
        this.threadLocal = Thread.currentThread();
    }

    /**
     * 
unlock
     */
    public void unlock(){
        if(value.get() == 0){
            return;
        }
        if(threadLocal == Thread.currentThread())
            value.compareAndSet(1,0);
    }

}

TryLock 测试类 TryLockTest.java

public class TryLockTest {
    private static CompareAndSetLock lock = new CompareAndSetLock();

    public static void main(String[] args) {
        for (int i = 0; i < 5; i++) {
            new Thread(){
                @Override
                public void run() {
                    try {
                        doSomething();
                    } catch (GetTryLockException e) {
                        //e.printStackTrace();
                        System.out.println("get lock fail >>> do other thing.");
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }.start();
        }
    }

    private static void doSomething() throws GetTryLockException, InterruptedException {
        try {
            lock.tryLock();
            System.out.println(Thread.currentThread().getName()+" get lock success.");
            Thread.sleep(100_0000);
        }finally {
            lock.unlock();
        }
    }
}

获取锁自定义异常类GetTryLockException.java

public class GetTryLockException extends Exception {
  public GetTryLockException() {
      super();
  }
  public GetTryLockException(String message) {
      super(message);
  }
}

运行结果

Thread-0 get lock success.
get lock fail >>> do other thing.
get lock fail >>> do other thing.
get lock fail >>> do other thing.
get lock fail >>> do other thing.