JAVA多线程变量的深入认识(三)_java thread 独立变量

现在的问题来了，当我们关注例子I，希望共享类RunInstance，即
    RunInstance t = new RunInstance();
        Thread t1 = new Thread(t);
        Thread t2 = new Thread(t);
却又要对变量进行线程单独化的管理时，怎么办？这时候就有了ThreadLocal。请看
例子III
首先我们对类TestInstance做一下改造，也就是把Flag变成ThreadLocal，即线程的独自变量
改造如下1,2,3点，接着我们仍旧运行例子I
class TestInstance {
    static Integer count = 0;
    //1: public int flag = 0;
    public ThreadLocal flag = new ThreadLocal(){
        public Integer initialValue(){
            return 0;
        }
    };

    public void runtest(){
    //2:  if (flag ==0)m1();  
        if (flag.get() ==0)m1();  
        else   m2();
        }
    public  void m1(){
    //3.  flag=1;
        flag.set(1);
        synchronized(count){
        for(int i = 0;i < 10; i++){
            count++;   
            System.out.println(Thread.currentThread().getName()+": m1's printing : count = "+count);  
            }
        }
    }
    public void m2(){
        synchronized(count){    
            for(int i = 0;i < 10; i++){
                count++;  
                System.out.println(Thread.currentThread().getName()+": m2's printing : count = "+count);  
            }  
        }
    }
}
却发现结果发生了变化。两个线程都只执行了m1，也就是说flag是
线程独立的。
Thread-0: m1's printing : count = 2
Thread-1: m1's printing : count = 2
Thread-0: m1's printing : count = 3
Thread-1: m1's printing : count = 4
Thread-0: m1's printing : count = 5
Thread-1: m1's printing : count = 6
Thread-0: m1's printing : count = 7
Thread-1: m1's printing : count = 8
Thread-0: m1's printing : count = 9
Thread-1: m1's printing : count = 10
Thread-0: m1's printing : count = 11
Thread-1: m1's printing : count = 12
Thread-0: m1's printing : count = 13
Thread-1: m1's printing : count = 14
Thread-0: m1's printing : count = 15
Thread-1: m1's printing : count = 16
Thread-0: m1's printing : count = 17
Thread-1: m1's printing : count = 18
Thread-0: m1's printing : count = 19
Thread-1: m1's printing : count = 20