< H2 > the first case < / H2 >

package com.btmans.thread;

public class TestSync implements Runnable{
    int b = 100;
    public synchronized void m1() throws Exception{
        b = 1000;
        Thread.sleep(5000);
        System.out.println("b="+b);
        
    }
    public synchronized void m2() throws Exception{
        Thread.sleep(3000);
        b = 2000;
    }
    @Override
    public void run() {
        // TODO Auto-generated method stub
        try {
            m1();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    public static void main(String[] args) throws Exception {
        
        TestSync ts = new TestSync();
        Thread t = new Thread(ts);
        t.start();
        ts.m2();
        System.out.println("=="+ts.b);
        
    }
}

the output result is
= = 1000
baked 1000

< H2 > the second case: add the following red code < / H2 >

package com.btmans.thread;

public class TestSync implements Runnable{
    int b = 100;
    public synchronized void m1() throws Exception{
        System.out.println("m1");""
        b = 1000;
        Thread.sleep(5000);
        System.out.println("b="+b);
        
    }
    public synchronized void m2() throws Exception{
        System.out.println("m2");""
        Thread.sleep(3000);
        b = 2000;
    }
    @Override
    public void run() {
        // TODO Auto-generated method stub
        try {
            m1();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    
    public static void main(String[] args) throws Exception {
        
        TestSync ts = new TestSync();
        Thread t = new Thread(ts);
        t.start();
        ts.m2();
        System.out.println("=="+ts.b);
        
    }
}

then the result is sometimes
m2
M1
= 1000
baked 1000
sometimes it is
m2
M1
= 2000
baked 1000

this makes me have a big head. I only add an output statement. Why will it change if I add it? With the addition of "synchronized", what is the order in which the code is executed? I don"t understand.