Java实现：工厂有一头母牛,一年生一头小母牛,小母牛五年后可以生小牛,问20年工厂有多少头牛?

文件Mooooo。java如下：import java。util。ArrayList; public class Mooooo { public static void main(String[] args) { ArrayList cows = new ArrayList(); cows。add(new Cow(4)); for (int i = 0; i < 20; i++) { ArrayList newCows = new ArrayList(); for (Cow cow : cows) { cow。happyBirthday(newCows); } cows。addAll(newCows); } System。out。println("二十年共有牛 " + cows。size() + " 头。"); } }文件Cow。java如下：import java。util。ArrayList; public class Cow { private int age = 0; public Cow(int age) { this。age = age; } public void happyBirthday(ArrayList cows) { age++; if (age >= 4) { cows。add(new Cow(0)); } } } 计算出结果是907头牛,已调试成功,若有不明之处可联系我。