权重随机算法Java实现

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;  
        }  
    }  

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