Java实现随机券抽取示例

import java.util.*;
import java.util.concurrent.atomic.AtomicReference;

public class Main {
    static MapcouponList = new HashMap<>();

    public static void main(String[] args) {
        int totalCouponCount = 10000;//券总数量，由后台设定的各面额券的数量总和。如10块100张，20的50张，50的15张，100的5张，共170张。
        CouponItem couponItem;
        //初始化优惠券列表
        for (int i = 1; i <= totalCouponCount; i++) {
            couponItem = new CouponItem();
            couponItem.index = i;//优惠券id
            couponItem.couponid = "Coupon-" + i;//优惠券id
            couponList.put(i, couponItem);
        }
        //将Map中的键存储到List中
        ListkeyList = new ArrayList<>(couponList.keySet());
        //使用Collections.shuffle()方法对List进行随机排序
        Collections.shuffle(keyList);
        //创建一个新的Map集合
        MapshuffledMap = new LinkedHashMap<>();
        //根据打乱后的顺序重新构建Map集合
        for (Integer key : keyList) {
            shuffledMap.put(key,couponList.get(key));
        }
        couponList=shuffledMap;//将打乱的结果放回列表
        //取券操作
        Random random;
        CouponItem validitem;
        int errcount = 0;
        System.out.println("券总量：" + totalCouponCount);
        //循环取1000次券
        for (int i = 0; i <= totalCouponCount - 1; i++) {
            System.out.print("模拟第 " + (i + 1) + " 次取券。");
            try {
                validitem = getValidCoupon();
                System.out.println("取到券：index=" + validitem.getIndex() + ";couponid=" + validitem.getCouponid() + ";券剩余：" + (couponList.size()) + "张");
            } catch (Exception e) {
                errcount++;
                System.out.println("领券失败");
            }
        }
        System.out.println("取券结束,累计失败：" + errcount + "次");
    }

    //取有效券
    public static CouponItem getValidCoupon() {
        CouponItem _couponItem = null;
        CouponItem _curItem;
        if (couponList.size() == 1) {
            //最后一张
            for (Map.Entryitem : couponList.entrySet()) {
                _couponItem = item.getValue();
                couponList = new HashMap<>();
            }
        } else {
            Random random = new Random();
            int index = random.nextInt(couponList.size() - 1);
            int startindex = 1;
            int key = 0;
            Iteratoriterator = couponList.keySet().iterator();
            while (iterator.hasNext()) {
                key = iterator.next();
                startindex++;
                if (startindex >= index) {
                    _curItem = couponList.get(key);
                    _couponItem = _curItem;//取到对应的券
                    iterator.remove();
                    break;
                }
            }
        }
        return _couponItem;//返回取到的券
    }
}

public class CouponItem {
    int index;
    String couponid;
    public String getCouponid() {
        return couponid;
    }

    public void setCouponid(String couponid) {
        this.couponid = couponid;
    }

    public int getIndex() {
        return index;
    }

    public void setIndex(int index) {
        this.index = index;
    }
}