java wait阻塞_wait/notify问题，为什么程序会阻塞？

如下代码，执行多次，大部分程序会阻塞，不知道问题出现在哪，求教？

public class Main {

public static void main(String[] args) {

Serve s = new Serve();

Thread t1 = new Thread(new ThreadA(s));

Thread t2 = new Thread(new ThreadB(s));

t1.start();

t2.start();

}

}

class Serve {

private int count = 0;

private boolean hasCount = false;

public synchronized void addCount(int addCount) throws InterruptedException {

if(hasCount) {

wait();

System.out.println("add阻塞");

}else {

this.count += addCount;

hasCount = true;

notifyAll();

System.out.println("存钱，余额：" + this.count);

}

}

public synchronized void removeCount(int removeCount ) throws InterruptedException {

if(hasCount) {

this.count -= removeCount;

hasCount = false;

notifyAll();

System.out.println("取钱，余额：" + this.count);

}else {

wait();

System.out.println("remove阻塞");

}

}

}

class ThreadA implements Runnable {

private Serve s;

public ThreadA(Serve s) {

this.s = s;

}

@Override

public void run() {

for (int i = 0; i < 100; i++) {

try {

System.out.println("add" + i);

s.addCount(100);

} catch (InterruptedException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

}

}

class ThreadB implements Runnable {

private Serve s;

public ThreadB(Serve s) {

this.s = s;

}

@Override

public void run() {

for (int i = 0; i < 100; i++) {

try {

System.out.println("remove" + i);

s.removeCount(100);

} catch (InterruptedException e) {

e.printStackTrace();

}

}

}

}