java抽奖算法

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

import org.springframework.stereotype.Service;

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;

/**
 * 转盘抽奖逻辑
 * 
 * @author zwm
 * @date 2017-05-11
 */
@Service
public class LotteryTool {

	public static void main(String[] args) {
		List<Award> awards = new ArrayList<>();
		awards.add(new Award("a1", 0.1f, 10));
		awards.add(new Award("a2", 0.2f, 0));
		awards.add(new Award("a3", 0.3f, 10));
		awards.add(new Award("a4", 0.05f, 10));
		awards.add(new Award("a5", 0.2f, 100));
		for (int i = 0; i < 10; i++) {
			System.out.println("恭喜您，抽到了：" + lottery(awards).id);
		}
	}

	public static Award lottery(List<Award> awards) {
		// 总的概率区间
		float totalPro = 0f;
		// 存储每个奖品新的概率区间
		List<Float> proSection = new ArrayList<Float>();
		proSection.add(0f);
		// 遍历每个奖品，设置概率区间，总的概率区间为每个概率区间的总和
		for (Award award : awards) {
			// 每个概率区间为奖品概率乘以1000（把三位小数转换为整）再乘以剩余奖品数量
			totalPro += award.probability * 1000 * award.count;
			proSection.add(totalPro);
		}
		// 获取总的概率区间中的随机数
		Random random = new Random();
		float randomPro = (float) random.nextInt((int) totalPro);
		// 判断取到的随机数在哪个奖品的概率区间中
		for (int i = 0, size = proSection.size(); i < size; i++) {
			if (randomPro >= proSection.get(i) && randomPro < proSection.get(i + 1)) {
				return awards.get(i);
			}
		}
		return null;
	}

	static class Award {
		/** 编号 */
		public String id;
		/** 概率（0.1代表10%，最多3位小数，即千分之一级） */
		public float probability;
		/** 数量（该类奖品剩余数量） */
		public int count;

		public Award(String id, float probability, int count) {
			super();
			this.id = id;
			this.probability = probability;
			this.count = count;
		}

		public Award() {

		}
	}
}