02-类和对象-跟踪类对象创建个数

 1 public class DuiXiang {
 2     public static void main(String args[]) {
 3         TongJi x=new TongJi();
 4         x.shuchu();
 5         TongJi y=new TongJi();
 6         y.shuchu();
 7         TongJi z=new TongJi();
 8         z.shuchu();
 9     }
10 
11 }
12 class TongJi{
13     static int sum=0;
14     TongJi(){
15         sum++;
16     }
17     public void shuchu() {
18         System.out.println("你已创建"+sum+"个对象。");
19     }
20 }