Java练习 经典的兔子问题

好久没写Java代码，太生疏了。找些练习做做，温故而知新 - 递归很实用。

package edu.rob.prac;

import java.util.LinkedList;

/**
 * 
 * 【程序1】 
 *  题目：古典问题：有一只兔子，从出生后第3个月起每个月都生一只兔子，小兔子长到第三个月后每个月又生一
 *  只兔子，假如兔子都不死，问每个月的兔子总数为多少？ 
 *
 */

public class Practice_001 {

	public static void main(String[] args) {

		// Check each amount of all rabbits for the 1st to 10th month 
		for(int currentMonth=1; currentMonth<=10; currentMonth++) {

			Rabbit r = new Rabbit(1);
			r.setDirectChildren(currentMonth);

			System.out.println("The " + currentMonth + " Month :	" + r.getFamilyMemebersAmt());
		}

	}

}

class Rabbit {

	private int birthday;
	private LinkedList<Rabbit> directChildren = new LinkedList<Rabbit>();

	public Rabbit() {}

	public Rabbit(int birthday) {
		this.birthday = birthday;
	}

	// Set direct children base on current month and birthday of this rabbit
	public void setDirectChildren(int currentMonth) {

		Rabbit r;
		int month = currentMonth;

		// Add direct children if it has
		while ( month - this.birthday > 1) {
			r = new Rabbit(month);
			r.setDirectChildren(currentMonth);
			this.directChildren.add(r);
			month--;
		}

	}

	// get amount of all children and this rabbit 
	public int getFamilyMemebersAmt() {

		int familyMembersAmt = 1;

		for(Rabbit r:this.directChildren) {
			familyMembersAmt += r.getFamilyMemebersAmt();
		}

		return familyMembersAmt;
	}

	/**
	 * @return the directChildren
	 */
	public LinkedList<Rabbit> getDirectChildren() {
		return this.directChildren;
	}

	/**
	 * @param directChildren the directChildren to set
	 */
	public void setDirectChildren(LinkedList<Rabbit> children) {
		this.directChildren = children;
	}

	/**
	 * @return the birthday
	 */
	public int getBirthday() {
		return birthday;
	}

	/**
	 * @param birthday the birthday to set
	 */
	public void setBirthday(int birthday) {
		this.birthday = birthday;
	}

}

下面是程序运行结果。

The 1 Month :	1
The 2 Month :	1
The 3 Month :	2
The 4 Month :	3
The 5 Month :	5
The 6 Month :	8
The 7 Month :	13
The 8 Month :	21
The 9 Month :	34
The 10 Month :	55