main方法中设置线程优先级,子线程优先级也发生改变

[ChillChilling]

package thread;

public class TT implements Runnable {
	int b = 100;
	public synchronized void m1() throws InterruptedException{
		System.out.println(Thread.currentThread().getName()+" m1()的优先级 "+Thread.currentThread().getPriority());
		System.out.println("m1()1: b = " + b);
		b = 1000;
		System.out.println("m1()2: b = " + b);
		//Thread.sleep(400);
		//System.out.println("m1(): b = " + b);
	}
	
	public  void m2() throws InterruptedException{
		System.out.println(Thread.currentThread().getName()+" m2()的优先级 "+Thread.currentThread().getPriority());
		//Thread.sleep(100);
		System.out.println("m2()1: b = " + b);
		b = 2000;
		System.out.println("m2()2: b = " + b);
	}
	@Override
	public void run() {
		try {
			m1();
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}
	public static void main(String[] args) throws InterruptedException {
		Thread.currentThread().setPriority(Thread.MIN_PRIORITY);
		TT tt = new TT();
		Thread thread = new Thread(tt);
		
		thread.setPriority(Thread.MAX_PRIORITY);
		System.out.println(Thread.currentThread().getName()+Thread.currentThread().getPriority());
		
		thread.start();
		tt.m2();

		System.out.println(tt.b);
	}
}

执行结果有多种：
main1
main m2()的优先级 1
m2()1: b = 100
Thread-0 m1()的优先级 10
m1()1: b = 2000
m1()2: b = 1000
m2()2: b = 2000//有问题了，为什么不是1000
1000
执行结果 m1()1 b=2000，说明m2()的修改操作已经进行，然后m1()的修改操作也进行了，最后b应该为1000，为什么m2()2的b还可以变成2000。
-------------------------------
main1
main m2()的优先级 1
m2()1: b = 100
m2()2: b = 2000
Thread-0 m1()的优先级 10
m1()1: b = 2000
m1()2: b = 1000
2000//有问题了，为什么不是1000
-------------------
main1
main m2()的优先级 1
m2()1: b = 100
m2()2: b = 2000
2000
Thread-0 m1()的优先级 10
m1()1: b = 2000
m1()2: b = 1000
正常
----------------------
main1
main m2()的优先级 1
m2()1: b = 100
Thread-0 m1()的优先级 10
m1()1: b = 2000
m2()2: b = 2000
1000
m1()2: b = 1000
m2修改为2000，m2()2输出后，m1修改为1000，main输出tt.b，m1()2输出

[ChillChilling]

main1 main m2()的优先级 1 Thread-0 m1()的优先级 10 m1()1: b = 100 m1()2: b = 1000 //m1()已经将b修改为1000 m2()1: b = 100 //为何还会输出b=100 m2()2: b = 2000 2000

[soton_dolphin]

引用 1 楼 BaiJJMM 的回复:

main1 main m2()的优先级 1 Thread-0 m1()的优先级 10 m1()1: b = 100 m1()2: b = 1000 //m1()已经将b修改为1000 m2()1: b = 100 //为何还会输出b=100 m2()2: b = 2000 2000

变量b 被两个线程共享，在执行m1的线程还没有完成的时候，m2（）里面看到b的值不一定会被更新。如果你在m2()上面也加syncrhonized 就没事儿了。 还有线程优先级只是给cpu一个提示，并不会控制cpu执行线程的顺序。

[ChillChilling]

题目起错了，应该是线程执行出现了混乱。。求各为大大解答！