java实现权重随机算法

权重随机算法在抽奖，资源调度等系统中应用还是比较广泛的，一个简单的按照权重来随机的实现，权重为几个随机对象(分类)的命中的比例，权重设置越高命中越容易，之和可以不等于100；

简单实现代码如下：

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

    public class WeightRandom {
        static List<WeightCategory>  categorys = new ArrayList<WeightCategory>();
        private static Random random = new Random();  

        public static void initData() {
            WeightCategory wc1 = new WeightCategory("A",60);
            WeightCategory wc2 = new WeightCategory("B",20);
            WeightCategory wc3 = new WeightCategory("C",20);
            categorys.add(wc1);
            categorys.add(wc2);
            categorys.add(wc3);
        }  

        public static void main(String[] args) {
              initData();
              Integer weightSum = 0;
              for (WeightCategory wc : categorys) {
                  weightSum += wc.getWeight();
              }  

              if (weightSum <= 0) {
               System.err.println("Error: weightSum=" + weightSum.toString());
               return;
              }
              Integer n = random.nextInt(weightSum); // n in [0, weightSum)
              Integer m = 0;
              for (WeightCategory wc : categorys) {
                   if (m <= n && n < m + wc.getWeight()) {
                     System.out.println("This Random Category is "+wc.getCategory());
                     break;
                   }
                   m += wc.getWeight();
              }  

        }  

    }  

    class WeightCategory {
        private String category;
        private Integer weight;  

        public WeightCategory() {
            super();
        }  

        public WeightCategory(String category, Integer weight) {
            super();
            this.setCategory(category);
            this.setWeight(weight);
        }  

        public Integer getWeight() {
            return weight;
        }  

        public void setWeight(Integer weight) {
            this.weight = weight;
        }  

        public String getCategory() {
            return category;
        }  

        public void setCategory(String category) {
            this.category = category;
        }
    }