正确停止线程的方法

package com.lhy.thread;

public class ThreadStop {

    public static void main(String[] args) {
        Runner r  = new Runner();
        Thread t = new Thread(r);
        t.start();
        for(int i=0;i<100;i++){
            System.out.println("main thread i="+i);
        }
        System.out.println("main thread is over!");
        r.shutDown();
    }

}

class Runner implements Runnable {
    private boolean flag = true;

    public void run() {

        int i = 0;
        while (flag) {
            System.out.println("i= "+i);
            i++;
        }
    }
    public void shutDown(){
        flag = false;
        System.out.println("Runner thread is over!");
    }

}