JAVA概率抽奖
礼物奖品类package com;
import java.math.BigDecimal;
/**
* 奖品类
* @author:rex
* @date:2014年10月20日
* @version:1.0
*/
public class Gift {
private int index;
private String gitfId;
private String giftName;
private double probability;
public Gift(int index, String gitfId, String giftName, double probability) {
this.index = index;
this.gitfId = gitfId;
this.giftName = giftName;
this.probability = probability;
}
public int getIndex() {
return index;
}
public void setIndex(int index) {
this.index = index;
}
public String getGitfId() {
return gitfId;
}
public void setGitfId(String gitfId) {
this.gitfId = gitfId;
}
public String getGiftName() {
return giftName;
}
public void setGiftName(String giftName) {
this.giftName = giftName;
}
public double getProbability() {
return probability;
}
public void setProbability(double probability) {
this.probability = probability;
}
@Override
public String toString() {
return "Gift [礼物索引=" + index + ", 礼物id=" + gitfId + ", 礼物价格=" + giftName + ", 礼物概率="
+new BigDecimal(probability+"")+ "]";
}
}
概率算法类
package com;
;
import java.math.BigDecimal;
import java.util.Collections;
import java.util.List;
import java.util.Random;
public class Lottory {
private Random rm = new Random();
public class AwardConfig {
///probaility 为概率0.2 即 20% 得概率0.05即5%的中奖概率
private BigDecimal probaility;
///奖品名称
private String name;
public BigDecimal getProbaility() {
return probaility;
}
public void setProbaility(BigDecimal probaility) {
this.probaility = probaility;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
public String reward(List<AwardConfig> giftList) {
if (giftList == null || giftList.isEmpty()) {
return null;
}
// 按照概率排序（如果不排序，下面随机数的区间需要做其他处理，否则无法己算正确的概率分布）
Collections.sort(giftList, (o1, o2) -> {
if (o1.getProbaility().doubleValue() > o2.getProbaility().doubleValue()) {
return 1;
} else if (o1.getProbaility().doubleValue() == o2.getProbaility().doubleValue()) {
return 0;
} else {
return -1;
}
});
BigDecimal[] probabilityList = new BigDecimal;
int index = 0;
BigDecimal allRate = BigDecimal.valueOf(0);
String targetNumber = "";
for (AwardConfig gift : giftList) {
probabilityList = gift.getProbaility();
allRate = allRate.add(gift.getProbaility());
index++;
if (gift.getProbaility().compareTo(BigDecimal.ONE) == 0) {
/// 如果单个奖品概率等于1，直接中该奖品
System.out.println("如个奖品概率等于1，直接中该奖品.");
return gift.getName();
}
String proStr = gift.getProbaility().toString();
String proStrTemp = proStr.substring(proStr.indexOf(".") + 1);
if (proStrTemp.length() > targetNumber.length()) {
/// 找到小数位最长的那个概率配置
targetNumber = proStrTemp;
}
}
// if (allRate.intValue() != 1) {
// ///这里可以设置 所有奖品得概率总和必须为100%，当然也可以是其他数字，根据区间匹配。
// System.out.println("概率相加不等于1.");
// return null;
// }
BigDecimal basicNumber = null;
if (targetNumber != null && targetNumber.equals("") == false) {
basicNumber = BigDecimal.valueOf(Math.pow(10, targetNumber.length()));
}
int diceRoll = rm.nextInt(basicNumber.intValue());
if (diceRoll < 0) {
System.err.println("随机数字小于0.");
return null;
}
BigDecimal cumulative = BigDecimal.ZERO;
for (int i = 0; i < giftList.size(); i++) {
AwardConfig luckGift = giftList.get(i);
if (luckGift != null && luckGift.getProbaility().compareTo(BigDecimal.ZERO) > 0) {
cumulative = cumulative.add(luckGift.getProbaility().multiply(basicNumber));
///如果随机出得数字区间落在该奖品得区间内，即中得该奖品。这块得实现可以修改，只要数字区间为奖品区间就可以。
if (diceRoll <= cumulative.intValue()) {
return giftList.get(i).getName();
}
}
}
return null;
}
}
主类
package com;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* 不同概率抽奖
* @author:rex
* @date:2014年10月20日
* @version:1.0
*/
public class LotteryTest {
public static void main(List<Gift> gifts,String GiftName,Double probability,Double SubStract) {
gifts = new ArrayList<Gift>();
// 序号==物品Id==物品名称==概率
// GiftName="52000";
// probability=(Double) 0.002;
gifts.add(new Gift(1, "P1", GiftName, probability));
gifts.add(new Gift(2, "P2", "没中",(Double)(1-probability)));
// gifts.add(new Gift(3, "P3", "物品3", 0.4d));
// gifts.add(new Gift(4, "P4", "物品4", 0.3d));
// gifts.add(new Gift(5, "P5", "物品5", 0d));
// gifts.add(new Gift(6, "P6", "物品6", -0.1d));
// gifts.add(new Gift(7, "P7", "物品7", 0.008d));
List<Double> orignalRates = new ArrayList<Double>(gifts.size());
for (Gift gift : gifts) {
double probability1 = gift.getProbability();
if (probability1 < 0) {
probability1 = 0;
}
orignalRates.add(probability1);
}
// statistics
Map<Integer, Integer> count = new HashMap<Integer, Integer>();
double num = 1;
for (int i = 0; i < num; i++) {
int orignalIndex = LotteryUtil.lottery(orignalRates);
Integer value = count.get(orignalIndex);
count.put(orignalIndex, value == null ? 1 : value + 1);
}
for (Map.Entry<Integer, Integer> entry : count.entrySet()) {
System.out.println((gifts.get(entry.getKey()) + ", count=" + entry.getValue() + ", probability="
+ entry.getValue() / num));
System.out.println(gifts.get(entry.getKey()).getGiftName().equals(GiftName));
System.out.println("----------------");
// + entry.getValue() / num));
}
}
public static void main(String[] args) {
main(new ArrayList<Gift>(),"52000",(Double)0.002,0.01);
}
}
使用方法,把以上代码放入你所在项目,然后调用main,传入相关参数即可开始抽奖
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