软件大赛题目----（第九个）求牛的数目

package com.bird.software;

import java.util.ArrayList;
import java.util.List;

public class Cow {
private int age;

public Cow afterYears(){
age++;
return age > 2 ? new Cow() : null;
}

public static void showTotalCowNum(int n){
List<Cow> list = new ArrayList<Cow>();
list.add(new Cow());

for(int i = 0; i < n; i++){
int cowCount = list.size();
for(int j = 0; j < cowCount; j++){
Cow cow = list.get(j).afterYears();
if(cow != null){
++cowCount;
list.add(cow);
}
}
}

System.out.println(n+"年后，共有："+list.size()+"头牛");
}

public static void main(String[] args){
showTotalCowNum(5);
}
}