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  categorys = new ArrayList();
	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;
	}
}