权重概率计算,app翻牌子后台的设计,随机抽奖,电商app用

package com.demo.utils;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import org.junit.Test;

/**
 * 	计算所有商品概率的总权重,然后在做区间,之后在判断属于哪个区间
 * 	在对应获取奖品的index
 * @ClassName: LotteryProbability
 * @Description: 权重概率  电商抽奖类型
 * @Author Crazy
 * @DateTime 2019年12月14日 上午11:43:49
 */
public class LotteryProbability {
	
	@Test
	public void test() throws NoSuchMethodException, SecurityException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
		List<Gift> prizes = new ArrayList<>();
		prizes.add(new Gift("谢谢惠顾", 95));
		prizes.add(new Gift("50金币", 0.8));
		prizes.add(new Gift("iphone x手机", 0.01));
		prizes.add(new Gift("华为手机", 0.19));
		prizes.add(new Gift("10金币", 4));
		//查询到的数据乱序,翻牌子后页面上展示的顺序就每次不同
		Collections.shuffle(prizes); 
		int index = lottery(prizes);
		System.out.println("我抽到了:"+prizes.get(index).getName());
		prizes.forEach(p ->{
			System.out.println(p.getName());
		});
		System.out.println("-------页面点击的是第三张牌,两张牌位置互换----------");
		Collections.swap(prizes,3-1,index);
		prizes.forEach(p ->{
			System.out.println(p.getName());
		});

	}
	
	
	
	
	
	public static void main(String[] args) throws NoSuchMethodException, SecurityException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
		
		List<Gift> prizes = new ArrayList<>();
		prizes.add(new Gift("谢谢惠顾", 95));
		prizes.add(new Gift("50金币", 0.8));
		prizes.add(new Gift("iphone x手机", 0.01));
		prizes.add(new Gift("华为手机", 0.19));
		prizes.add(new Gift("10金币", 4));
		int p0 = 0, p1 = 0, p2 = 0, p3 = 0, p4 =0;
		long start = System.currentTimeMillis();
		int total = 100;
		for(int i = 0; i< total; i++) {
			int lottery = lottery(prizes);
			if(lottery == 0) {
				p0++;
			}else if(lottery == 1) {
				p1++;
			}else if(lottery == 2) {
				p2++;
			}else if(lottery == 3) {
				p3++;
			}else if(lottery == 4) {
				p4++;
			}
			
		}
		System.out.println(p0+"人抽到:"+prizes.get(0).getName());
		System.out.println(p1+"人抽到:"+prizes.get(1).getName());
		System.out.println(p2+"人抽到:"+prizes.get(2).getName());
		System.out.println(p3+"人抽到:"+prizes.get(3).getName());
		System.out.println(p4+"人抽到:"+prizes.get(4).getName());
		start = System.currentTimeMillis() - start;
		System.out.println("参与人数: " + total + ", 耗时: " + start + "ms");
		int index = lottery(prizes);
		System.out.println("我抽到了:"+prizes.get(index).getName());
		Gift gift = prizes.get(index);
		prizes.forEach(p ->{
			System.out.println(p.getName());
		});
		//我点击的第三个牌子 
		prizes.add(3, gift);
		prizes.forEach(p ->{
			System.out.println(p.getName());
		});

	}
	/**
	 * 
	 * @Title: lottery
	 * @Description: 抽奖
	 * @Author Crazy
	 * @DateTime 2019年12月14日 上午11:47:34
	 * @param prizes 任何需要概率计算的对象（T：必须为拥有probability属性的对象或数值型对象
	 * @param field具体概率字段名（实体对象默认probability，数值型对象可不传）
	 * @return  prizes 列表的中奖index, -1 则表示抽奖失败
	 * @throws SecurityException 
	 * @throws NoSuchMethodException 
	 * @throws InvocationTargetException 
	 * @throws IllegalArgumentException 
	 * @throws IllegalAccessException 
	 */
	public static<T> int lottery(List<T> prizes,String... field) throws NoSuchMethodException, SecurityException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
		if(prizes == null || prizes.isEmpty()) {
			return -1;
		}
		
		int size = prizes.size();
		String f = "probability";
		T t = prizes.get(0);
		boolean isBasicType = false;
		if(t instanceof Double || t instanceof Float || t instanceof String) {
			isBasicType = true;
		}else {
			if(field != null && field.length > 0 ) {
				f = field[0];
			}
		}
		
		//计算总概率,这样可以保证不一定总概率是1 
		double sumRate = 0d;
		List<Double> orignalRates = new ArrayList<>(size);
		for(T gift :prizes) {
			double probability = 0;
			if(isBasicType) {
				probability = Double.parseDouble(gift.toString());
				
			}else {
				Method method = gift.getClass().getMethod("get"+f.substring(0, 1).toUpperCase()+f.substring(1));
				Object invoke = method.invoke(gift);
				if(invoke != null) {
					probability = Double.parseDouble(invoke.toString());
				}
			}
			if(probability < 0) {
				probability = 0;
			}
			sumRate += probability;
			orignalRates.add(probability);
		}
		//计算每个物品在总概率的基础下的概率情况(构建区间,核心部分)
		List<Double> sortOrignalRates = new ArrayList<>(size);
		Double tempSumRate = 0d;
		for(double rate : orignalRates) {
			tempSumRate += rate;
			sortOrignalRates.add(tempSumRate / sumRate);
			
		}
		//根据区间值来获取抽取到的物品索引,理论上random随机概率是均等,因此区间的大
		//小决定了概率大小
		double nextDouble = Math.random();
		sortOrignalRates.add(nextDouble);
		Collections.sort(sortOrignalRates);
		return sortOrignalRates.indexOf(nextDouble);
		
		
	}
	
	
	
	
	
	static class Gift{
		private String name;
		private double probability;
		private int total;
		private int count;
		
		public Gift() {
			super();
		}
		public Gift(String name, double probability) {
			super();
			this.name = name;
			this.probability = probability;
		}
		public String getName() {
			return name;
		}
		public void setName(String name) {
			this.name = name;
		}
		public double getProbability() {
			return probability;
		}
		public void setProbability(double probability) {
			this.probability = probability;
		}
		public int getTotal() {
			return total;
		}
		public void setTotal(int total) {
			this.total = total;
		}
		public int getCount() {
			return count;
		}
		public void setCount(int count) {
			this.count = count;
		}
		
	}
	
	
	
	
	
	

}