奖品类：

抽奖逻辑：

测试类：

测试结果：

商品类：

package org.plusgroup.modules.app.controller.vo;

import io.swagger.annotations.ApiModelProperty;
import lombok.Data;

import java.util.ArrayList;
import java.util.List;

/**
 * @author Administrator
 * @desc 奖品VO
 * @date 2022/7/9 14:30
 */
@Data
public class PrizeVo {
    @ApiModelProperty("奖品ID")
    private Integer id;
    @ApiModelProperty("奖品名称")
    private String name;
    @ApiModelProperty("奖品编号")
    private String code;
    @ApiModelProperty("中奖概率")
    private Double rate;

    public PrizeVo(Integer id, String name, String code, Double rate) {
        this.id = id;
        this.name = name;
        this.code = code;
        this.rate = rate;
    }
    public PrizeVo() {
    }

    /**
     * 初始化奖品
     * @return List
     */
    public static List init(){
        List list = new ArrayList();
        list.add(new PrizeVo(10, "文档打印券", "P1", 0.2d));
        list.add(new PrizeVo(20, "照片打印券", "P2", 0.5d));
        list.add(new PrizeVo(30, "5元代金券", "P3", 0.1d));
        list.add(new PrizeVo(40, "谢谢参与", "P4", 0.2d));
        return list;
    }
}

测试类：

package org.plusgroup.modules.admin.service;

import org.plusgroup.modules.app.controller.vo.PrizeVo;
import org.springframework.util.CollectionUtils;

import java.util.*;

/**
 * @author Administrator
 * @desc
 * @date 2022/7/9 14:43
 */
public class IntegralLogTest {

    public static void main(String [] args){
        //奖品中奖概率集合
        List rates = new ArrayList();
        //将每个奖品的概率放入概率集合
        List list = PrizeVo.init();
        for(PrizeVo prizeVo : list){
            rates.add(prizeVo.getRate());
        }
        System.out.println("本次中奖商品下标:" +luckDraw(rates));

        // 统计每种商品中奖次数
        Map countMap = new HashMap();
        double num = 10000; //测试次数
        for (int i = 0; i  entry : countMap.entrySet()) {
            System.out.println(list.get(entry.getKey()) + ", 命中次数=" + entry.getValue() + ", 实际概率=" + entry.getValue() / num);
        }
    }


    /**
     * 抽奖逻辑
     * @param rates 概率集合
     * @return int
     */
    public static int luckDraw(List rates) {
        if (CollectionUtils.isEmpty(rates)) {
            return -1;
        }
        //计算总概率，概率集合累加
        double totalRate = 0d;
        for (double rate : rates) {
            totalRate += rate;
        }
        // 每个奖品在总概率基础下的概率
        List sortRates = new ArrayList();
        double everyRate = 0d;
        for (double rate : rates) {
            everyRate += rate;
            sortRates.add(everyRate / totalRate);
        }
        // 根据区块值来获取抽取到的物品索引
        double nextDouble = Math.random();
        sortRates.add(nextDouble);
        Collections.sort(sortRates);

        return sortRates.indexOf(nextDouble);
    }
}