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：

importjava.util.ArrayList;

importjava.util.List;

importjava.util.Random;  

publicclass WeightRandom {

    staticList<WeightCategory>  categorys = newArrayList<WeightCategory>();

    privatestatic Random random = newRandom();  

    publicstatic void initData() {

        WeightCategory wc1 = newWeightCategory("A",60);

        WeightCategory wc2 = newWeightCategory("B",20);

        WeightCategory wc3 = newWeightCategory("C",20);

        categorys.add(wc1);

        categorys.add(wc2);

        categorys.add(wc3);

    } 

    publicstatic 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();

          } 

    } 

} 

classWeightCategory {

    privateString category;

    privateInteger weight;  

    publicWeightCategory() {

        super();

    } 

    publicWeightCategory(String category, Integer weight) {

        super();

        this.setCategory(category);

        this.setWeight(weight);

    } 

    publicInteger getWeight() {

        returnweight;

    } 

    publicvoid setWeight(Integer weight) {

        this.weight = weight;

    } 

    publicString getCategory() {

        returncategory;

    } 

    publicvoid setCategory(String category) {

        this.category = category;

    }

}