Semaphore semaphore = new Semaphore(1);
semaphore.release();
System.out.println(semaphore.availablePermits());
// 输出为2，信号量变多了

protected final boolean tryReleaseShared(int releases) {
	for (; ; ) {
		int current = getState();
		int next = current + releases;

		if (next < current) // overflow
			throw new Error("Maximum permit count exceeded");

		// 如果释放的信号量超过容量，则设定为容量的大小
		if (next > capacity)
			next = capacity;

		if (compareAndSetState(current, next))
			return true;
    }
}