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;            }        }