JAVA使用随机数实现概率抽奖

本文实例为大家分享了JAVA使用随机数实现概率抽奖的具体代码，供大家参考，具体内容如下

需求

网站现有一抽奖功能，已经定义好奖品，每个奖品都有对应的中奖概率。通过奖品概率随机进行抽奖

实现思路

1、每个奖品都有对应的中奖概率，先对所有奖品中奖概率求和
2、计算出每个奖品在0-1之间所占的区间块
3、随机产生0-1之间的随机数，随机数落在哪个区间，就是中奖哪个
例如现有以下奖品：
奖品A 中奖概率为 0.1
奖品B 中奖概率为 0.01
奖品C 中奖概率为 0.001
奖品D 中奖概率为 0.8

第一步：求出概率总和 0.1+0.01+0.001+0.8 = 0.911

第二步：计算每个奖品的所占区间块

奖品A： 0.1 / 0.911 = 0.1098
奖品B： （0.1+0.01）/ 0.911 = 0.1207
奖品C：（0.1+0.11+0.001）/ 0.911 = 0.1218
奖品D：（0.1+0.11+0.001+0.8）/ 0.911 = 1

则：

奖品A的所占区间为：0~0.1098
奖品B的所占区间为：0.1098~0.1207
奖品C的所占区间为：0.1207~0.1218
奖品D的所占区间为：0.1218~1

代码如下

public class Award{
  public Award(){}
  public Award(String awardTitle,double probability){
    this.awardTitle = awardTitle;
    this.probability = probability;
  }
  
  private String awardId;
  
  private String awardTitle;
  
  private double probability;
  public String getAwardId() {
    return awardId;
  }
  public void setAwardId(String awardId) {
    this.awardId = awardId;
  }
  public String getAwardTitle() {
    return awardTitle;
  }
  public void setAwardTitle(String awardTitle) {
    this.awardTitle = awardTitle;
  }
  public double getProbability() {
    return probability;
  }
  public void setProbability(double probability) {
    this.probability = probability;
  }
}

public class LotteryUtil {

  
  public static Award lottery(List awardList) {
    if(awardList.isEmpty()){
      throw new AwardListIsEmptyException();
    }
    //奖品总数
    int size = awardList.size();

    //计算总概率
    double sumProbability = 0d;
    for (Award award : awardList) {
      sumProbability += award.getProbability();
    }

    //计算每个奖品的概率区间
    //例如奖品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 sortAwardProbabilityList = new ArrayList(size);
    Double tempSumProbability = 0d;
    for (Award award : awardList) {
      tempSumProbability += award.getProbability();
      sortAwardProbabilityList.add(tempSumProbability / sumProbability);
    }

    //产生0-1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
    sortAwardProbabilityList.add(randomDouble);
    Collections.sort(sortAwardProbabilityList);
    int lotteryIndex = sortAwardProbabilityList.indexOf(randomDouble);
    return awardList.get(lotteryIndex);
  }

  public static void main(String[] args) {
    List awardList = new ArrayList();
    awardList.add(new Award("10个积分",0.35d));
    awardList.add(new Award("33个积分",0.25d));
    awardList.add(new Award("5元红包",0.002d));
    awardList.add(new Award("20元话费",0.003d));
    awardList.add(new Award("京东100元购物卡",0.0005d));
    awardList.add(new Award("未中奖",0.1d));

    Map result = new HashMap();
    for(int i=0;i<10000;i++){
      Award award = lottery(awardList);
      String title = award.getAwardTitle();
      Integer count = result.get(title);
      result.put(title, count == null ? 1 : count + 1);
    }

    for (Entry entry : result.entrySet()) {
      System.out.println(entry.getKey() + ", count=" + entry.getValue() +", reate="+ entry.getValue()/10000d);
    }
  }
}

测试结果

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持考高分网。