农夫养牛

package excise;import java.util.ArrayList;import java.util.List;/**  * 问题描述：  *   * 一头母牛在3—10岁的时候每年可以生一头小牛，生公牛和母牛的比率是50%，  * 在牛12岁的时候就送入屠宰场买了。现在有一个农夫有1头1岁大的母牛，  * 在母牛3岁的时候就送到附近的农场去配种，请问40年后这个农夫可能会有多少头牛，  * 写出相关的代码或答题思路，最好用面向对象。  *  */ public class ComputeCattles {// 保存所有母牛private static List<Cattle> cows = new ArrayList<Cattle>();// 保存所有当前农夫拥有的牛private static List<Cattle> cattles = new ArrayList<Cattle>();public static void main(String[] args) {// 第一头母牛Cattle cow = new Cattle(0, 3);cows.add(cow);for (int i = 0; i < 40; ++i) {// 40年// 每年，所有的牛，大于等于12岁的牛送到屠宰场卖掉for (int j = 0; j < cattles.size(); ++j) {Cattle temp = cattles.get(j);if (temp.getDead()) {cattles.remove(temp);}// 所有牛都在长cattles.get(j).grow();}// 一头母牛生一头小牛for (int j = 0; j < cows.size(); ++j) {Cattle calf = cows.get(j).bear();if (calf != null) {if (calf.getSex() == 0)cows.add(calf);cattles.add(calf);}}}System.out.println("40年后农夫可能拥有" + cattles.size() + "头牛");}}class Cattle {private int sex;private int age;private boolean dead = false;public Cattle() {}public Cattle(int sex, int age) {this.sex = sex;this.age = age;}public Cattle bear() {Cattle calf = null;if (this.sex == 0) {calf = birth();}return calf;}private Cattle birth() {Cattle calf = null;if (this.age >= 3 && this.age <= 10) {calf = new Cattle(random(), 0);}return calf;}private int random() {return (int) Math.round(Math.random());}public void grow() {this.age++;}public int getSex() {return this.sex;}public boolean getDead() {if (this.age >= 12)dead = true;return this.dead;}}