设计4个线程 其中两个线程每次对j增加1

public class ThreadTest1 {

private int j;
public static void main(String args[]) {
ThreadTest1 tt = new ThreadTest1();
Inc inc = tt.new Inc();//Inc()内部类，使用内部类是因为j是全局变量
Dec dec = tt.new Dec();//Dec()内部类
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 < 10; i++) {
inc();
}
}
}

class Dec implements Runnable {
public void run() {
for (int i = 0; i < 10; i++) {
dec();
}
}
}
}