使用java實(shí)現(xiàn)一個(gè)微信紅包功能

/**
 * 紅包類
 * @author mrchai
 *
 */
public class RedPacket {

 /**紅包ID*/
 private int id;
 /**紅包金額*/
 private BigDecimal money;
 
 public RedPacket() {
 }

 public RedPacket(int id, BigDecimal money) {
 super();
 this.id = id;
 this.money = money;
 }

 public int getId() {
 return id;
 }

 public void setId(int id) {
 this.id = id;
 }

 public BigDecimal getMoney() {
 return money;
 }

 public void setMoney(BigDecimal money) {
 this.money = money;
 }

 @Override
 public String toString() {
 return id+"號(hào)用戶獲得"+money+"元";
 }
 
}

/**
 * 紅包異常
 * @author mrchai
 */
public class RedpacketException extends Exception{

 public RedpacketException() {
 // TODO Auto-generated constructor stub
 }
 
 public RedpacketException(String msg) {
 super(msg);
 }
}

package com.softeem.lesson18.RedPacket;

import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.Random;

public class RedPacketManage {

 /** 設(shè)置每個(gè)紅包最小金額 */
 static final BigDecimal MIN = new BigDecimal("0.01");

 /*
 * @double total 總金額
 * @int count 紅包個(gè)數(shù)
 * @return 返回生成的所有紅包金額集合
 */
 public static ArrayList<RedPacket> genRedPacket(double total, int count) throws RedPacketException {
 // 聲明臨時(shí)變量用于存儲(chǔ)所有隨機(jī)的紅包對(duì)象
 ArrayList<RedPacket> packets = new ArrayList<RedPacket>();
 // 計(jì)算每個(gè)紅包分配最低金額一共需要多少錢
 double min = MIN.multiply(new BigDecimal(count)).setScale(2, BigDecimal.ROUND_HALF_EVEN).doubleValue();
 if (min > total) {
  // 紅包金額不夠分配時(shí)，拋出異常
  throw new RedPacketException("每個(gè)紅包金額不能少于0.01元");
 } else if (min == total) {
  // 紅包金額恰好每人只夠分配0.01元，則平均分配
  for (int i = 0; i < count; i++) {
  // 創(chuàng)建紅包對(duì)象
  RedPacket item = new RedPacket(i + 1, new BigDecimal("0.01"));
  // 將紅包加入集合
  packets.add(item);
  }
 } else {
  // 當(dāng)總金額大于每人最少金額之和時(shí)，隨機(jī)分配
  // 將總金額包裝為BigDecimal
  BigDecimal totalMoney = new BigDecimal(total);
  
  //先為每人分配最低金額0.01元
  //避免因?yàn)榭偨痤~太少導(dǎo)致有紅包金額為0
  for(int i=0;i<count;i++) {
  packets.add(new RedPacket(i+1, new BigDecimal("0.01")));
  }
  //將總金額設(shè)置為在原來(lái)基礎(chǔ)上減去每人最低分配金額
  totalMoney = totalMoney.subtract(new BigDecimal(min));
  
  //聲明臨時(shí)變量統(tǒng)計(jì)當(dāng)前分配的金額總數(shù)
  BigDecimal now = new BigDecimal(0);
  // 獲取每個(gè)紅包的比例
  double[] scale = randomScale(count);
  // 為前count-1個(gè)紅包分配金額
  for (int i = 0; i < count - 1; i++) {
  // 獲取當(dāng)前比例紅包需要分配的金額
  BigDecimal item = totalMoney.multiply(new BigDecimal(scale[i]))
      .setScale(2, BigDecimal.ROUND_HALF_EVEN);
  //為每人在最低金額基礎(chǔ)上增加隨機(jī)比例金額
  packets.get(i).setMoney(packets.get(i).getMoney().add(item));
  //累計(jì)已分配金額總數(shù)
  now = now.add(item);
  }
  // 剩余的金額給最后一個(gè)
  //獲取剩余的金額
  BigDecimal last = totalMoney.subtract(now);
  //設(shè)置最后一個(gè)紅包的金額為原來(lái)基礎(chǔ)上增加剩余的總金額
  packets.get(count-1).setMoney(packets.get(count-1).getMoney().add(last).setScale(2, BigDecimal.ROUND_HALF_EVEN));
 }
 return packets;
 }

 /**
 * 隨機(jī)紅包金額比例
 * @param count 紅包的份數(shù)
 * @return 每份紅包的比例數(shù)組
 */
 private static double[] randomScale(int count) {
 // 臨時(shí)數(shù)組存儲(chǔ)所有紅包的金額比例
 double[] scale = new double[count];
 Random r = new Random();
 double total = 0.0;
 for (int i = 0; i < count; i++) {
  // 為每一個(gè)元素設(shè)置一個(gè)1-100隨機(jī)數(shù)
  scale[i] = r.nextInt(100) + 1;
  // 累計(jì)所有隨機(jī)的數(shù)值
  total += scale[i];
 }
 // 循環(huán)計(jì)算每個(gè)紅包的金額比例
 for (int i = 0; i < count; i++) {
  scale[i] = scale[i] / total;
 }
 return scale;
 }

 public static void main(String[] args) throws RedPacketException {
 ArrayList<RedPacket> list = genRedPacket(0.1, 5);
 BigDecimal t = new BigDecimal(0);
 for (RedPacket rp : list) {
  System.out.println(rp);
  t= t.add(rp.getMoney());
 }
 System.out.println(t);
 }
}

public static void main(String[] args) throws RedpacketException {
  ArrayList<RedPacket> list = genRedPacket(0.1, 5);
  BigDecimal t = new BigDecimal(0);
  for (RedPacket rp : list) {
    System.out.println(rp);
    t= t.add(rp.getMoney());
  }
  System.out.println(t);
}