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 zzg;

public class ThreadTest {
private int j;
public static void main(String[] arge){
    ThreadTest t1 = new ThreadTest();
    Inc inc = t1.new Inc();
    Dec dec = t1.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() + "-inc:" + 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();
        }
    }
}
}