Java根據概率、剩餘獎品數量動態抽獎算法實現，概率總和可以不爲100%

1、建立獎品類，獎品類中只有三種基本屬性編號、中獎機率、獎品剩餘數量。

public class Award {
    /**編號*/
    public String id;
    /**概率（0.1代表10%，最多3位小數，即千分之一級）*/
    public float probability;
    /**數量（該類獎品剩餘數量）*/
    public int count;

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

    public Award(){

    }
}

2、實現抽獎算法，整個算法很簡單，基本思想是根據概率和剩餘獎品數量來分配一個空間，再在這個空間中取隨機數，判斷隨機數落在哪個區塊方法獲得抽獎結果。

public static Award lottery(List<Award> awards){
        //總的概率區間
        float totalPro = 0f;
        //存儲每個獎品新的概率區間
        List<Float> proSection = new ArrayList<Float>();
        proSection.add(0f);
        //遍歷每個獎品，設置概率區間，總的概率區間爲每個概率區間的總和
        for (Award award : awards) {
            //每個概率區間爲獎品概率乘以1000（把三位小數轉換爲整）再乘以剩餘獎品數量
            totalPro += award.probability * 10 * award.count;
            proSection.add(totalPro);
        }
        //獲取總的概率區間中的隨機數
        Random random = new Random();
        float randomPro = (float)random.nextInt((int)totalPro);
        //判斷取到的隨機數在哪個獎品的概率區間中
        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;
    }

3、測試抽獎算法，寫一段簡單的代碼測試一下以上代碼。
分兩種情況：
1）數量相同

public static void main(String[] args) {
        List<Award> awards = new ArrayList<>();
        awards.add(new Award("a1",0.1f,100));
        awards.add(new Award("a2",0.2f,100));
        awards.add(new Award("a3",0.3f,100));
        awards.add(new Award("a4",0.05f,100));
        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);
        }
    }

2）數量不同

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,100));
        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);
        }
    }