import java.util.ArrayList;
import java.util.List;
import java.util.Random;
 
/**
 * 抽獎工具類,概率和可以不等于1
 * 概率為百分數去掉百分號的部分，如10%，則為10
 * 抽獎操作如下：
 * 1.輸入抽獎概率集合，【抽獎概率集合為{10.0, 20.0, 30.0}】
 * 2.生成連續(xù)集合，  【生成的連續(xù)集合為{(0.0, 10.0],(10.0, 30.0],(30.0, 60.0]}】
 * 3.生成隨機數，   【生成方法為 random.nextDouble() * maxElement】
 * 4.判斷隨機數在哪個區(qū)間內，返回該區(qū)間的index【生成了隨機數12.001，則它屬于(10.0, 30.0]，返回 index = 1】
 * 
 */
public class LotteryUtil {
 
 /**
 * 定義一個連續(xù)集合
 * 集合中元素x滿足:(minElement,maxElement]
 * 數學表達式為：minElement < x <= maxElement
 *
 */
 public class ContinuousList {
 
 private double minElement;
 private double maxElement;
 
 public ContinuousList(double minElement, double maxElement){
 if(minElement > maxElement){
 throw new IllegalArgumentException("區(qū)間不合理，minElement不能大于maxElement！");
 }
 this.minElement = minElement;
 this.maxElement = maxElement;
 }
 
 /**
 * 判斷當前集合是否包含特定元素
 * @param element
 * @return
 */
 public boolean isContainKey(double element){
 boolean flag = false;
 if(element > minElement && element <= maxElement){
 flag = true;
 }
 return flag;
 }
 
 }
 
 private List<ContinuousList> lotteryList; //概率連續(xù)集合
 private double maxElement;  //這里只需要最大值，最小值默認為0.0
 
 /**
 * 構造抽獎集合
 * @param list 為獎品的概率
 */
 public LotteryUtil(List<Double> list){
 lotteryList = new ArrayList<ContinuousList>();
 if(list.size() == 0){
 throw new IllegalArgumentException("抽獎集合不能為空！");
 }
 double minElement = 0d;
 ContinuousList continuousList = null;
 for(Double d : list){
 minElement = maxElement;
 maxElement = maxElement + d;
 continuousList = new ContinuousList(minElement, maxElement);
 lotteryList.add(continuousList);
 }
 }
 
 /**
 * 進行抽獎操作
 * 返回：獎品的概率list集合中的下標
 */
 public int randomColunmIndex(){
 int index = -1;
 Random r = new Random();
 double d = r.nextDouble() * maxElement; //生成0-1間的隨機數
 if(d == 0d){
 d = r.nextDouble() * maxElement;  //防止生成0.0
 }
 int size = lotteryList.size();
 for(int i = 0; i < size; i++){
 ContinuousList cl = lotteryList.get(i);
 if(cl.isContainKey(d)){
 index = i;
 break;
 }
 }
 if(index == -1){
 throw new IllegalArgumentException("概率集合設置不合理！");
 }
 return index;
 
 }
 
 public double getMaxElement() {
 return maxElement;
 }
 
 public List<ContinuousList> getLotteryList() {
 return lotteryList;
 }
 public void setLotteryList(List<ContinuousList> lotteryList) {
 this.lotteryList = lotteryList;
 }
 
 
}

package com.lottery;
 
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
 
class Result{
 private int index;
 private int sumTime;
 private int time;
 private double probability;
 private double realProbability;
 
 public int getIndex() {
 return index;
 }
 
 public void setIndex(int index) {
 this.index = index;
 }
 
 public int getTime() {
 return time;
 }
 
 public void setTime(int time) {
 this.time = time;
 }
 
 public int getSumTime() {
 return sumTime;
 }
 
 public void setSumTime(int sumTime) {
 this.sumTime = sumTime;
 }
 
 public double getProbability() {
 return probability;
 }
 
 public double getRealProbability() {
 return realProbability;
 }
 
 public void setRealProbability(double realProbability) {
 this.realProbability = realProbability;
 }
 
 public Result(){
 
 }
 
 public Result(int index, int sumTime, int time, double realProbability) {
 this.setIndex(index);
 this.setTime(time);
 this.setSumTime(sumTime);
 this.setRealProbability(realProbability);
 
 }
 
 public String toString(){
 return "索引值：" + index + "，抽獎總數：" + sumTime + "，抽中次數：" + time + "，概率：" 
   + realProbability + "，實際概率：" + (double)time/sumTime;
 }
}
 
public class TestLottery {
 
 static final int TIME = 100000;
 
 public static void iteratorMap(Map<Integer, Integer> map, List<Double> list){
 for(Entry<Integer, Integer> entry : map.entrySet()){
 int index = entry.getKey();
 int time = entry.getValue();
 Result result = new Result(index, TIME, time, list.get(index));
 System.out.println(result);
 }
 }
 
 public static void main(String[] args) {
 //構造概率集合
 List<Double> list = new ArrayList<Double>();
 list.add(20d);
 list.add(80d);
 list.add(50d);
 list.add(30d);
 LotteryUtil ll = new LotteryUtil(list);
 double sumProbability = ll.getMaxElement();
 
 Map<Integer, Integer> map = new HashMap<Integer, Integer>();
 for(int i = 0; i < TIME; i++){
 int index = ll.randomColunmIndex();
 if(map.containsKey(index)){
 map.put(index, map.get(index) + 1);
 }else{
 map.put(index, 1);
 }
 }
 for(int i = 0; i < list.size(); i++){
 double probability = list.get(i) / sumProbability;
 list.set(i, probability);
 }
 iteratorMap(map, list);
 
 }

}