Java实现按比抽奖功能

 /**
   * 按比例随机抽取一项
   * @param list 奖品列表
   * @return 类型值
   */
  public static String ratioExtract(List<Prize> list) {
    //非空判断
    if (list==null || list.size()<1) {
      return null;
    }
    //占比之和
    double sum=0.00;
    //分段数组(20,30,60)
    double[] subArray=new double[list.size()+1];
    //将概率分段
    for (int i = 0; i < list.size(); i++) {
      subArray[i]=sum;
      //这里除要考虑奖品所占比重外还要将奖品数量计算分段其中
      sum+=list.get(i).getPrizeWeight()*list.get(i).getPrizeCount();
    }
    //加上取最大的值
    subArray[subArray.length-1]=sum;

    /* 产生随机数 */
    Random random=new Random();
    double rand = random.nextDouble()*sum;

    //返回字符
    String field=null;
    for (int i = 0; i < subArray.length; i++) {
      if (i==subArray.length-1) {
        return field;
      }
      if (rand>=subArray[i] && rand<subArray[i+1]) {
        field=list.get(i).getPrizeName();
        break;
      }
    }
    return field;
  }

import lombok.Data;
import org.apache.commons.lang.math.RandomUtils;

import java.util.List;
import java.util.Random;

/**
 * @Description: 抽奖工具类
 * @author: xiake
 * @Date: 2020/1/5 13:23
 * @ModifiedDate：2020/1/5 13:23
 * @Copyright: miaoxaike.com
 */
public class PrizeMathRandom {

  /**
   * 按比例随机抽取一项
   * @param fieldArray 类型值数组
   * @param proportions 与类型值对应 的占比值
   * @return 类型值
   */
  public static String ratioExtract(String[] fieldArray,double[] proportions) {
    //判断两个数组长度是否相等
    if(fieldArray.length!=proportions.length) {
      return "两数组长度不相等,无法执行";
    }

    //占比之和
    double sum=0.00;
    //分段数组(20,30,60)
    double[] subArray=new double[proportions.length+1];
    //将概率分段
    for (int i = 0; i < proportions.length; i++) {
      subArray[i]=sum;
      sum+=proportions[i];
    }
    //加上取最大的值
    subArray[subArray.length-1]=sum;
    Random random=new Random();
    /* 产生随机数 区间为 (0,sum)*/
    double rand = random.nextDouble()*sum;
    //返回字符
    String field=null;
    for (int i = 0; i < subArray.length; i++) {
      if (rand>=subArray[i] && rand<subArray[i+1]) {
        field=fieldArray[i];
      }
    }
    return field;
  }

  /**
   * 按比例随机抽取一项
   * @param list 奖品列表
   * @return 类型值
   */
  public static String ratioExtract(List<Prize> list) {
    //非空判断
    if (list==null || list.size()<1) {
      return null;
    }
    //占比之和
    double sum=0.00;
    //分段数组(20,30,60)
    double[] subArray=new double[list.size()+1];
    //将概率分段
    for (int i = 0; i < list.size(); i++) {
      subArray[i]=sum;
      sum+=list.get(i).getPrizeWeight()*list.get(i).getPrizeCount();
    }
    //加上取最大的值
    subArray[subArray.length-1]=sum;

    /* 产生随机数 */
    Random random=new Random();
    double rand = random.nextDouble()*sum;

    //返回字符
    String field=null;
    for (int i = 0; i < subArray.length; i++) {
      if (i==subArray.length-1) {
        return field;
      }
      if (rand>=subArray[i] && rand<subArray[i+1]) {
        field=list.get(i).getPrizeName();
        break;
      }
    }
    return field;
  }


  /**
   * 双重分段抽取,
   * @param fieldArray 分段数组, 参数值用"-"组装(例: {"6-14","14-23","23-32","32-40"})
   * @param proportions 每段出现的概率
   * @return 返回按比例抽取后, 分段范围内的随机一个值
   */
  public static Integer ratioExtractDouble(String[] fieldArray,double[] proportions) {
    String string = ratioExtract(fieldArray,proportions);
    String[] split = string.split("-");
    int result = RandomUtils.nextInt(Integer.parseInt(split[1]))+Integer.parseInt(split[0]);
    return result;
  }

  @Data
  @NoArgsConstructor
  @AllArgsConstructor
  class Prize{
    //奖品名称
    private String prizeName;
    //奖品占比
    private double prizeWeight;
    //奖品数量
    private int prizeCount;
  }
}

public static void main(String[] args) {
    //初始化奖品信息
    List<Prize> prizeList=new ArrayList<>();
    prizeList.add(new Prize("一等奖",1,1));
    prizeList.add(new Prize("二等奖",3,4));
    prizeList.add(new Prize("三等奖",6,5));

    for (int i = 0; i < 12; i++) {
      Prize prize = ratioExtract(prizeList);
      if (prize!=null){
        System.out.println("第"+(i+1)+"次,抽中 "+prize.getPrizeName()+" 剩余奖品数量="+prize.getPrizeCount());
      }else {
        System.out.println("第"+(i+1)+"次,奖品已抽完");
      }

    }
  }