Java抽奖算法第二例_java_--HTML5中文学习网

本文实例为大家分享了java抽奖算法，供大家参考，具体内容如下

1. 算法分析
根据概率将奖品划分区间，每个区间代表一个奖品，然后抽取随机数，反查落在那个区间上，即为所抽取的奖品。

2. 代码
核心算法

public class Arithmetic {  // 放大倍数  private static final int mulriple = 1000000;  public int pay(List<Prize> prizes) {    int lastScope = 0;    // 洗牌，打乱奖品次序    Collections.shuffle(prizes);    Map<Integer, int[]> prizeScopes = new HashMap<Integer, int[]>();    Map<Integer, Integer> prizeQuantity = new HashMap<Integer, Integer>();    for (Prize prize : prizes) {      int prizeId = prize.getPrizeId();      // 划分区间      int currentScope = lastScope + prize.getProbability().multiply(new BigDecimal(mulriple)).intValue();      prizeScopes.put(prizeId, new int[] { lastScope + 1, currentScope });      prizeQuantity.put(prizeId, prize.getQuantity());      lastScope = currentScope;    }    // 获取1-1000000之间的一个随机数    int luckyNumber = new Random().nextInt(mulriple);    int luckyPrizeId = 0;    // 查找随机数所在的区间    if ((null != prizeScopes) && !prizeScopes.isEmpty()) {      Set<Entry<Integer, int[]>> entrySets = prizeScopes.entrySet();      for (Map.Entry<Integer, int[]> m : entrySets) {        int key = m.getKey();        if (luckyNumber >= m.getValue()[0] && luckyNumber <= m.getValue()[1] && prizeQuantity.get(key) > 0) {          luckyPrizeId = key;          break;        }      }    }    if (luckyPrizeId > 0) {      // 奖品库存减一    }    return luckyPrizeId;  }}

Prize bean

public class Prize {  /**   * 奖品唯一标示   */  private Integer prizeId;  /**   * 中奖概率   */  private BigDecimal probability;  /**   * 奖品数量   */  private Integer quantity;  public Integer getPrizeId() {    return prizeId;  }  public void setPrizeId(Integer prizeId) {    this.prizeId = prizeId;  }  public BigDecimal getProbability() {    return probability;  }  public void setProbability(BigDecimal probability) {    this.probability = probability;  }  public Integer getQuantity() {    return quantity;  }  public void setQuantity(Integer quantity) {    this.quantity = quantity;  }}

3. 测试

prize1概率: 5%
prize2概率: 10%

prize3概率: 15%
prize4概率: 20%

prize5概率: 50%

public class Test {  public static void main(String[] args) {    List<Prize> prizes = new ArrayList<Prize>();    Prize prize1 = new Prize();    prize1.setPrizeId(1);    prize1.setProbability(new BigDecimal(0.05));    prize1.setQuantity(1);    prizes.add(prize1);    Prize prize2 = new Prize();    prize2.setPrizeId(2);    prize2.setProbability(new BigDecimal(0.10));    prize2.setQuantity(10);    prizes.add(prize2);    Prize prize3 = new Prize();    prize3.setPrizeId(3);    prize3.setProbability(new BigDecimal(0.15));    prize3.setQuantity(20);    prizes.add(prize3);    Prize prize4 = new Prize();    prize4.setPrizeId(4);    prize4.setProbability(new BigDecimal(0.20));    prize4.setQuantity(50);    prizes.add(prize4);    Prize prize5 = new Prize();    prize5.setPrizeId(5);    prize5.setProbability(new BigDecimal(0.50));    prize5.setQuantity(200);    prizes.add(prize5);    int prize1GetTimes = 0;    int prize2GetTimes = 0;    int prize3GetTimes = 0;    int prize4GetTimes = 0;    int prize5GetTimes = 0;    Arithmetic arithmetic = new Arithmetic();    int times = 1000;    for (int i = 0; i < times; i++) {      int prizeId = arithmetic.pay(prizes);      switch (prizeId) {        case 1:          prize1GetTimes++;          break;        case 2:          prize2GetTimes++;          break;        case 3:          prize3GetTimes++;          break;        case 4:          prize4GetTimes++;          break;        case 5:          prize5GetTimes++;          break;      }    }    System.out.println("抽奖次数" + times);    System.out.println("prize1中奖次数" + prize1GetTimes);    System.out.println("prize2中奖次数" + prize2GetTimes);    System.out.println("prize3中奖次数" + prize3GetTimes);    System.out.println("prize4中奖次数" + prize4GetTimes);    System.out.println("prize5中奖次数" + prize5GetTimes);  }}

结果：

通过1000次抽取，我们看出算法精度还是很高的。

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。