课后作业10.13

public class Statistics {
    private static int n;
    public Statistics()
    {
        n++; //每次new一个对象是n+1
    }
    public static int getNum()
    {
        return n; //返回n值
    }
    public static void main(String[] args){
        Statistics s1=new Statistics();
        Statistics s2=new Statistics();
        Statistics s3=new Statistics(); 
        Statistics s4=new Statistics();//创建对象
        System.out.println("共有对象个数为："+Statistics.getNum());
    }

}