多线程编程题

package xmltest;

public class ThreadTest1 {
    private int j;
    public static void main(String args[]) {
        ThreadTest1 tt = new ThreadTest1();
        Inc inc = tt.new Inc();
        Dec dec = tt.new Dec();
        for (int i = 0; i < 2; i++) {
            Thread t = new Thread(inc);
            t.start();
            t = new Thread(dec);
            t.start();
        }
    }

    private synchronized void inc() {
        j++;
        System.out.println(Thread.currentThread().getName() + "-inc:" + j);
    }

    private synchronized void dec() {
        j--;
        System.out.println(Thread.currentThread().getName() + "-dec:" + j);
    }

    class Inc implements Runnable {
        public void run() {
            for (int i = 0; i < 100; i++) {
                inc();
            }
        }
    }


    class Dec implements Runnable {
        public void run() {
            for (int i = 0; i < 100; i++) {
                dec();
            }
        }
    }
}