public class JavaTest {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        System.out.println("main start");
        MyThread thread = new MyThread();
        Thread a = new Thread(thread, "A");
        Thread b = new Thread(thread, "B");
        a.start();
        b.start();

        System.out.println("main end");
    }

}

class MyThread implements Runnable {
    private int i = 0;

    @Override
    public void run() {
        // TODO Auto-generated method stub
        System.out.println(Thread.currentThread().getName() + " run enter i = " + i);
        synchronized(this){
            System.out.println(Thread.currentThread().getName() + " synchronized >>>>>>> i = " + i);
            for (; i < 5; i++) {
            //for (i = 0; i < 5; i++) {
                System.out.println(Thread.currentThread().getName() + " synchronized loop " + i);
            }
        }

        System.out.println(Thread.currentThread().getName() + " run exit");
    }

}