深入理解reentrantlock

private Lock lock = new ReentrantLock();
 
public void test(){
    lock.lock();
    try{
        do();
    }catch (Exception e){
        throw e;
    }finally {
        lock.unlock();
    }
}

final void lock() {
     //cas方法比较状态是否为1，如果为0，就把状态改为1，并获得锁
    if (compareAndSetState(0, 1))
        setExclusiveOwnerThread(Thread.currentThread());
    //否则就再次请求一次。
    else
        acquire(1);
}

/**抢占模式或者非公平锁*/
final boolean nonfairTryAcquire(int acquires) {
    final Thread current = Thread.currentThread();
    int c = getState();
    if (c == 0) { 
         //会在去比较一次
        if (compareAndSetState(0, acquires)) {
            setExclusiveOwnerThread(current);
            return true;
        }
        //是自己占有了锁，重入锁，那就可以再次获得锁，然后修改state
    } else if (current == getExclusiveOwnerThread()) { 
        int nextc = c + acquires;
        if (nextc < 0) // overflow
            throw new Error("Maximum lock count exceeded");
        setState(nextc);
        return true;
    }
    return false;
}