红包生成方案.txt

package com.well.wan.utils;

import com.alibaba.fastjson.JSONObject;
import com.google.common.collect.Lists;

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

/**
 * Created by Administrator on 2017/5/19.
 */
public class RedPacketUtil {

    /**
     * 计算每个红包的金额,并生成集合
     *
     * @param redPacketAmount
     * @param redPacketSize
     * @return
     */
    public static List
 
   getEachAmount(BigDecimal redPacketAmount, int redPacketSize) {
        List
  
    redPacketList = Lists.newLinkedList(); //算平均值 BigDecimal singleAmount = redPacketAmount.divide(new BigDecimal(redPacketSize),5,BigDecimal.ROUND_HALF_UP); //设置保底最小值 BigDecimal min = new BigDecimal("0.01"); //如果平均值等于0.01,所有红包为一分 int compareTo = singleAmount.compareTo(min); if (compareTo == 0) { for (int i = 0; i < redPacketSize; i++) { redPacketList.add(min); } return redPacketList; //如果平均值大于0.01,所有红包先保底0.01,总红包减去所有保底,然后再去分 }else if(compareTo == 1){ redPacketAmount = redPacketAmount.subtract(new BigDecimal(String.valueOf(redPacketSize)).multiply(min)); //如果小于0.01，说明红包的钱和红包的数量输入不合法 }else{ throw new RuntimeException("最小红包不能少于0.01"); } //如果红包数量为1或分到最后一个分到的就是剩下的所有钱加上保底0.01 while (redPacketSize > 0) { if (redPacketSize == 1) { redPacketSize--; redPacketAmount = redPacketAmount.add(min).setScale(2, BigDecimal.ROUND_HALF_UP); redPacketList.add(redPacketAmount); return redPacketList; } Random random = new Random(); //剩余红包钱求平均数乘以2，为最大值 BigDecimal max = redPacketAmount.divide(new BigDecimal(redPacketSize), BigDecimal.ROUND_HALF_UP).multiply(new BigDecimal("2")); //最大值乘以一个随机数，得到红包值 BigDecimal money = new BigDecimal(String.valueOf(random.nextDouble())).multiply(max); //判断生成的红包是否保底 int i = money.compareTo(min); if (i == -1 || i == 0) { money = min; redPacketList.add(money); //大于保底值 则加上保底 得到当前红包值 }else { redPacketAmount = redPacketAmount.subtract(money); money = money.add(min).setScale(2,BigDecimal.ROUND_HALF_UP); redPacketList.add(money); } redPacketSize--; } return redPacketList; } public static void main(String[] args) { BigDecimal redPacketAmount = new BigDecimal(0.05); int redPacketSize = 5; List
   
     redPacketList = getEachAmount(redPacketAmount, redPacketSize); BigDecimal sum = BigDecimal.ZERO; for (BigDecimal bigDecimal : redPacketList) { sum = sum.add(bigDecimal); } System.out.println(JSONObject.toJSONString(redPacketList)); System.out.println(sum); BigDecimal count=BigDecimal.ZERO; for(BigDecimal bigDecimal : redPacketList){ count = count.add(bigDecimal); } System.out.println(count.toString()); } } 有不足之处希望指点，这也是网络上大神的代码做了一些改进完成的，帖出来分享。