public class TestThread {
    public static void main(String[] args) {
        Runner r1 = new Runner();
        r1.flag = 1; //标示，运行m1方法
        Thread t1 = new Thread(r1);
        t1.start();
        
        Runner r2 = new Runner();
        r2.flag = 2; //标示，运行m2方法
        Thread t2 = new Thread(r2);
        t2.start();
    }
}
class Runner implements Runnable {
    static String str = "哈哈";
    int flag = 0;
    public void run() {
        try {
            if(flag == 1) {
                m1();
            }
            if(flag == 2) {
                m2();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    public void m1() throws Exception {
        synchronized(str) {
        str = "m1";
        Thread.sleep(1000);
        System.out.println("1:" + str);
        }
    }
    public void m2() throws Exception {
        synchronized(str) {
        str = "m2";
        Thread.sleep(1000);
        System.out.println("2:" + str);
        }
    }
}