Java多线程互斥访问变量

Java多线程互斥访问比较简单，在方法前面加上synchronize修饰则变为同步方法。下面是例子：

class WorkThread extends Thread{
    private CourruptedData data = null ;
    private int type = 0 ;
    public WorkThread(CourruptedData _data,int _type){
        data = _data ;
        type = _type ;
        super.start();
    }
    public void run(){
        data.performWork(type);
    }
}

public class CourruptedData {
    protected static int display = 1 ;
    protected static int change = 2 ;
    private WorkThread slowWorker = null ;
    private WorkThread fastWorker = null ;
    private int number = 0 ;

    public CourruptedData() {
        number = 1 ;
        slowWorker = new WorkThread(this,display);//-----------慢进程先启动;
        fastWorker = new WorkThread(this,change);
    }

    /*
     * 关键字为synchronized时，方法修饰为同步方法，
     * 慢线程调用performWokr()时，休眠两秒；
     * 此时，不允许第二个线程打断第一个线程；
     * 等第一个线程执行完毕之后，第二个线程才能将number改为-1；
     */

    public synchronized void performWork(int type){
        if (type == display)
        {
            System.out.println("Number before sleeping:" + number);
            try{
                slowWorker.sleep(2000);
            }catch (InterruptedException ie){
                System.out.println("Error : "+ie);
            }
            System.out.println("Number after working up:"+ number);
        }
        if (type == change)
            number = -1 ;
    }
    public static void main(String args[])
    {
        CourruptedData test = new CourruptedData();
    }
}

程序运行结果为：

当去掉performWork()方法的 synchronized 修饰之后，程序运行结果为：