Java 线程同步：如何解决主线程和子线程无法交替执行的问题？

public static void main(string[] args) {

    methread me = new methread();
    thread t = new thread(me);
    t.start();

    boolean flag = true;
    //修改了初始值
    int i = 0;

    synchronized (me) {
        while (flag) {
            system.out.println(thread.currentthread().getname() + i);
            i++;

            if (i % 100 == 0) {
                try {
                    //方便观察效果,睡眠1s
                    thread.sleep(1000);
                    system.out.println("main============");
                    //从finally代码块中前移到wait()方法前
                    me.notify();
                    //锁对象为me
                    me.wait();
                } catch (interruptedexception e) {
                    e.printstacktrace();
                }
            }
        }
    }
}

class MeThread implements Runnable {
    @Override
    public synchronized void run() {
        int i = 0;
        boolean flag = true;

        while (flag) {
            System.out.println(Thread.currentThread().getName() + i);
            i++;

            if (i % 10 == 0) {
                try {
                    //方便观察
                    Thread.sleep(1000);
                    System.out.println("MeThread============");
                    //同步方法锁对象为this,notify()移动到wait()方法前
                    this.notify();
                    //同步方法锁对象为this
                    this.wait();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}