JAVA使用随机数实现概率抽奖

 /** * 奖品实体类 */ public class Award{ public Award(){} public Award(String awardTitle,double probability){ this.awardTitle = awardTitle; this.probability = probability; } /**奖品ID**/ private String awardId; /**奖品名**/ private String awardTitle; /**中奖概率**/ 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 { /** * 抽奖，获取中奖奖品 * @param awardList 奖品及中奖概率列表 * @return 中奖商品 */ 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<mark style="color:transparent">来源gaodaimacom搞#^代%!码网</mark>.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); } } }