JAVA多线程(三个猴子分桃)操作,为什么总是出现一个线程，求大神！

public class ThreadDemo {

int mutex = 100;
boolean isRun = true;

int i = 0;

public static void main(String[] args) {

    Monkey m = new ThreadDemo().new Monkey();
    new Thread(m, "1").start();
    new Thread(m, "2").start();
    new Thread(m, "3").start();
}

class Monkey implements Runnable {

    @Override
    public  void run() {

        getTao();

    }

    public  void getTao() {

        while (isRun) {

            if (mutex % 2 == 0&&mutex!=0) {
                i = mutex;
                mutex = mutex / 2;
                System.out.println(Thread.currentThread().getName() + "de"
                        + mutex);
                mutex = i - mutex;
            } else if (mutex % 2 != 0) {
                i = mutex;
                mutex = mutex / 2 + 1;
                System.out.println(Thread.currentThread().getName() + "de"
                        + mutex);
                mutex = i - mutex;
            } else if (mutex == 0) {

                isRun = false;

            }
        }
    }
}

}