红包派送逻辑代码

package com.dbtest.test;

import java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.Scanner;

/**
 * @author Lizf on 2022/11/12.
 */
public class RedPacket {

    /**
     * 单个红包最大倍数
     */
    private static int MAX    = 2;

    /**
     * 单个红包最小数额
     */
    private static double MIN = 0.01;

    /**
     * 金额保留位数
     */
    private static DecimalFormat DECIMAL_FORMAT = new DecimalFormat(".00");


    public static void main(String[] args) {

        //金额
        double amount;
        //个数
        int    number;
        //平均数
        double avg;

        Scanner scanner = new Scanner(System.in);

        System.out.print("红包金额:");
        amount = scanner.nextDouble();

        System.out.print("红包个数:");
        number = scanner.nextInt();

        if ( number == 1 ) {
            System.out.println("¥："+amount);
            return;
        }

        //平均数
        avg = amount/number;

        if ( avg < MIN) {
            System.out.print("最少也要给一人一分吧！");
            return;
        }

        String str = DECIMAL_FORMAT.format(avg);
        avg = Float.parseFloat(str);

        List redPacket;
        while (true) {
            //生成红包
            List generateList = generate(number,avg);
            //校验红包
            redPacket = check(generateList,amount,number);
            //生成红包大于总金额重新生成
            if( redPacket.size() > 0) {
                break;
            }
        }
        redPacket.forEach( e -> {
            System.out.println("¥："+e);
        });

    }

    /**
     * 生成红包
     * @param number
     * @param avg
     * @return
     */
    private static List generate(double number, double avg) {
        List list = new ArrayList<>();
        for ( int i = 0; i < number; i++) {
            double result = (avg * Math.random()) * 2;
            //不在规则内, 重新生成
            while (result >= (avg * MAX) || result < MIN) {
                result = (avg * Math.random()) * 2;
            }
            list.add(Double.parseDouble(DECIMAL_FORMAT.format(result)));
        }
        return list;
    }

    /**
     * 校验红包
     * @param list
     * @param amount
     * @param number
     * @return
     */
    private static List check(List list, double amount, int number) {
        List resultList = new ArrayList<>();
        double total = 0;
        for (double d: list){
            total += d;
        }
        if ( total == amount ) {
            resultList = list;
        }

        //生成红包小于总金额
        if ( total < amount) {
            double sub = amount - total;
            int index = new Random().nextInt(number);
            for( int i = 0; i < number; i++){
                if( i == index) {
                    //多出来的随机指定到一个红包内
                    double newIndex = Double.parseDouble(DECIMAL_FORMAT.format(list.get(i)+sub));
                    resultList.add(newIndex);
                } else {
                    resultList.add(list.get(i));
                }
            }
        }
        return resultList;
    }
}