根据概率获取随机奖品

package com.sport.sportactivityserver.common.utils;

import com.sport.sportactivityserver.po.lottery.LyActivityLottery;
import lombok.extern.slf4j.Slf4j;
import org.springframework.util.StringUtils;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * create by zdj
 * time 2021/11/22
 */
@Slf4j
public class LotteryUtil {
    
    

  /**
   * 抽奖，获取中奖奖品
   * @param trailPrizeList 抽奖的奖品列表（里面要有奖品的概率哦）
   * @param name 抽奖用户
   * @return 中奖商品
   */
  public static LyActivityLottery lottery(List<LyActivityLottery> trailPrizeList, String name) {
    
    
    log.info("/*****************************开始抽奖*************************************/");
    if(!StringUtils.isEmpty(name)){
    
    
      log.info("/****** 抽奖用户名称："+name);
    }

    // 先计算出所有商品的总概率
    double sumProbability = 0d;
    for (LyActivityLottery award : trailPrizeList) {
    
    
      sumProbability += award.getProbability();
    }
    log.info("/****** 奖品总概率为：" + sumProbability);


    // 计算每个奖品的概率区间
    // eg:奖品A概率区间0-0.1 奖品B概率区间 0.1-0.5 奖品C概率区间0.5-1 [每个奖品的中奖率越大，所占的概率区间就越大]
    List<Double> sortPrizeProbabilityList = new ArrayList<Double>(trailPrizeList.size());
    double tempSumProbability = 0d;
    for (LyActivityLottery prize : trailPrizeList) {
    
    
      tempSumProbability += prize.getProbability(); // 当前商品的概率
      sortPrizeProbabilityList.add(tempSumProbability / sumProbability); // 当前商品在总概率中所占的概率权重
    }
    log.info("/****** 每个奖品对应的概率区间为：" + sortPrizeProbabilityList);


    //产生0-总概率之间的随机数
    //随机数在哪个概率区间内，则是哪个奖品
    double randomDouble = Math.random();
    //加入到概率区间中，排序后，返回的下标则是awardList中中奖的下标
    sortPrizeProbabilityList.add(randomDouble);
    log.info("/****** 随机数添加后【未排序】的区间：" + sortPrizeProbabilityList);

    Collections.sort(sortPrizeProbabilityList);
    log.info("/****** 随机数添加后【已排序】的区间：" + sortPrizeProbabilityList);

    int lotteryIndex = sortPrizeProbabilityList.indexOf(randomDouble);
    log.info("/****** 随机数所在的区间的下标：" + lotteryIndex);

    log.info("/****** 本次中奖奖品："+trailPrizeList.get(lotteryIndex).getName());
    log.info("/*****************************抽奖结束*************************************/");
    return trailPrizeList.get(lotteryIndex);
  }

  public static void main(String[] args) {
    
    
    List<LyActivityLottery> trailPrizeList = new ArrayList<>();
    LyActivityLottery lyActivityLottery = new LyActivityLottery();
    lyActivityLottery.setName("篮球");
    lyActivityLottery.setProbability(0.02);
    trailPrizeList.add(lyActivityLottery);

    LyActivityLottery lyActivityLottery2 = new LyActivityLottery();
    lyActivityLottery2.setName("空气");
    lyActivityLottery2.setProbability(0.02);
    trailPrizeList.add(lyActivityLottery2);

    LyActivityLottery lyActivityLottery3 = new LyActivityLottery();
    lyActivityLottery3.setName("兵乓球");
    lyActivityLottery3.setProbability(0.02);
    trailPrizeList.add(lyActivityLottery3);

    LyActivityLottery lyActivityLottery4 = new LyActivityLottery();
    lyActivityLottery4.setName("足球");
    lyActivityLottery4.setProbability(0.02);
    trailPrizeList.add(lyActivityLottery4);

    LyActivityLottery lyActivityLottery5 = new LyActivityLottery();
    lyActivityLottery5.setName("羽毛球");
    lyActivityLottery5.setProbability(0.02);
    trailPrizeList.add(lyActivityLottery5);
    lottery(trailPrizeList, "系统");
  }
}

测试：