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;  }  }