方法一：二倍均值法

import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
/**
 * 抢红包
 * </p>
 * <a href="https://juejin.im/post/5af80310f265da0b8636585e">参考</p>
 *
 * @author MinGRn <br > MinGRn97@gmail.com
 * @date 10/10/2018 09:48
 */
public class DivideRedPackage {
    /**
     * 发红包算法,金额参数以分为单位
     */
    private static List<Integer> divideRedPackage(Integer totalAmount, Integer totalPeopleNum) {
        List<Integer> amountList = new ArrayList<>();
        Integer restAmount = totalAmount;
        Integer restPeopleNum = totalPeopleNum;
        Random random = new Random();
        for (int i = 0; i < totalPeopleNum - 1; i++) {
            /*
             *随机范围：[1，剩余人均金额的两倍),左闭右开
             */
            int amount = random.nextInt(restAmount / restPeopleNum * 2 - 1) + 1;
            restAmount -= amount;
            restPeopleNum--;
            amountList.add(amount);
        }
        amountList.add(restAmount);
        return amountList;
    }
    public static void main(String[] args) {
        List<Integer> amountList = divideRedPackage(5000, 30);
        for (Integer amount : amountList) {
            System.out.println("抢到金额：" + new BigDecimal(amount).divide(new BigDecimal(100)));
        }
    }
}

参考:

• 漫画：如何实现抢红包算法?

方法二：

import java.util.Random;
/**
 * 抢红包
 * </p>
 * <a href="https://blog.csdn.net/lb_383691051/article/details/79379384">参考</p>
 *
 * @author MinGRn <br > MinGRn97@gmail.com
 * @date 10/10/2018 12:17
 */
public class DivideRedPackage {
    public static void main(String[] args) {
        Integer count = 10;
        Boolean isHave = true;
        MoneyPackage moneyPackage = new MoneyPackage((double) 100, 10);
        while (isHave) {
            if ((--count) <= 0) {
                isHave = false;
            }
            System.out.println(divideRedPackage(moneyPackage));
        }
    }
    /**
     * 随机获取红包
     *
     * @param moneyPackage 红包
     */
    private static double divideRedPackage(MoneyPackage moneyPackage) {
        if (moneyPackage.peopleNum == 1) {
            moneyPackage.peopleNum--;
            return (double) Math.round(moneyPackage.amount * 100) / 100;
        }
        double min = 0.01, max = moneyPackage.amount / moneyPackage.peopleNum * 2;
        double money = new Random().nextDouble() * max;
        money = money <= min ? min : money;
        money = Math.floor(money * 100) / 100;
        moneyPackage.peopleNum--;
        moneyPackage.amount -= money;
        return money;
    }
    static class MoneyPackage {
        /**
         * 红包总额
         */
        Double amount;
        /**
         * 红包数
         */
        Integer peopleNum;
        public Double getAmount() {
            return amount;
        }
        public void setAmount(Double amount) {
            this.amount = amount;
        }
        public Integer getPeopleNum() {
            return peopleNum;
        }
        public void setPeopleNum(Integer peopleNum) {
            this.peopleNum = peopleNum;
        }
        MoneyPackage(Double amount, Integer peopleNum) {
            this.amount = amount;
            this.peopleNum = peopleNum;
        }
    }
}

参考：

• 画家丶