设计4个线程，其中两个线程每次对j增加1，另外两个线程对j每次减少1

package com.yx.zzg;

public class ThreadTest1 {

   private AtomicInteger j=new AtomicInteger();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.incrementAndGet();
        System.out.println(Thread.currentThread().getName() + "-inc:" + j);
    }

    private synchronized void dec() {
        j.decrementAndGet();
        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();
            }
        }
    }

}