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();
}
}
}
}