java线程加锁运行顺序问题以及

Question

以下是我的测试对象加锁的代码，但是对运行出来的结果不太理解
public class Test0 implements Runnable {
int b = 100;

public synchronized void m1() throws Exception {
    b = 1000;
    System.out.println(b+1);
    Thread.sleep(5000);
    System.out.println("b=" + b);
}

public synchronized void m2() throws Exception {
    Thread.sleep(2500);
    b = 2000;
}

@Override
public void run() {
    try {
        m1();
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

public static void main(String[] args) throws Exception {

    Test0 test0 = new Test0();
    //System.out.println(test0.b);
    Thread t = new Thread(test0);
    t.start();
    test0.m2();
    System.out.println(test0.b);
    }
    }
    这是输出的结果
    ![图片说明](https://img-ask.csdn.net/upload/201705/26/1495802572_224813.png)希望大神解释以下程序运行的过程，实在不理解，为什么输出1001后又直接输出了1000

Answer 1

这个是运行结果