class Gym {

private int availableSpots = 10; // 健身中心初始有10个可用位置

// 预约位置

public synchronized void bookSpot(){

while (availableSpots <= 0) {

;

}

availableSpots--; // 预约一个位置

System.out.println(" has booked a spot. Spots available: " + availableSpots);

}

// 取消预约

public synchronized void cancelSpot() {

if (availableSpots < 10) {

availableSpots++; // 取消预约，增加一个位置

System.out.println(" has cancelled a spot. Spots available: " + availableSpots);

}

}

}

class GymMember implements Runnable {

private Gym gym;

private boolean book;

public GymMember(Gym gym, boolean book) {

this.gym = gym;

this.book = book;

}

@Override

public void run() {

if (book) {

gym.bookSpot();

for(int i=0;i<1000000;i++); // 模拟健身时间

gym.cancelSpot();

}

}

}

public class GymAppointmentSystem {

public static void main(String[] args) {

Gym gym = new Gym();

// 创建多个会员线程

Thread member1 = new Thread(new GymMember(gym, true));

Thread member2 = new Thread(new GymMember(gym, true));

Thread member3 = new Thread(new GymMember(gym, false)); // 这个会员只取消预约

member1.start();

member2.start();

member3.start();

}

}