Java权重随机的实现方法

/** 
 * 建议使用RandomUtil类创建RandomMeta对象 
 * @author wxf on 14-5-5. 
 */  
public class WeightMeta<T> {  
    private final Random ran = new Random();  
    private final T[] nodes;  
    private final int[] weights;  
    private final int maxW;  
  
    public WeightMeta(T[] nodes, int[] weights) {  
        this.nodes = nodes;  
        this.weights = weights;  
        this.maxW = weights[weights.length - 1];  
    }  
  
    /** 
     * 该方法返回权重随机对象 
     * @return 
     */  
    public T random() {  
        int index = Arrays.binarySearch(weights, ran.nextInt(maxW) + 1);  
        if (index < 0) {  
            index = -1 - index;  
        }  
        return nodes[index];  
    }  
  
    public T random(int ranInt) {  
        if (ranInt > maxW) {  
            ranInt = maxW;  
        } else if(ranInt < 0){  
            ranInt = 1;  
        } else {  
            ranInt ++;  
        }  
        int index = Arrays.binarySearch(weights, ranInt);  
        if (index < 0) {  
            index = -1 - index;  
        }  
        return nodes[index];  
    }  
  
    @Override  
    public String toString() {  
        StringBuilder l1 = new StringBuilder();  
        StringBuilder l2 = new StringBuilder("[random]\t");  
        StringBuilder l3 = new StringBuilder("[node]\t\t");  
        l1.append(this.getClass().getName()).append(":").append(this.hashCode()).append(":\n").append("[index]\t\t");  
        for (int i = 0; i < weights.length; i++) {  
            l1.append(i).append("\t");  
            l2.append(weights[i]).append("\t");  
            l3.append(nodes[i]).append("\t");  
        }  
        l1.append("\n");  
        l2.append("\n");  
        l3.append("\n");  
        return l1.append(l2).append(l3).toString();  
    }  
}

/** 
 * 随机工具类 
 * 
 * 使用权重的集合Map构建随机元数据对象 
 * 
 * 比如： 
 * 我们有3个url地址，他们的权重分别为1,2,3现在我们利用RandomUtil来根据权重随机获取url： 
 * 
 * <p><blockquote><pre> 
 * 
 * map.put(url1, 1); 
 * map.put(url2, 2); 
 * map.put(url3, 3); 
 * RandomMeta<String, Integer> md = RandomUtil.buildWeightMeta(map); 
 * String weightRandomUrl = md.random(); 
 * 
 * </pre></blockquote><p> 
 * 
 * @author wxf on 14-5-5. 
 */  
public class RandomUtil {  
    public static <T> WeightMeta<T> buildWeightMeta(final Map<T, Integer> weightMap) {  
        final int size = weightMap.size();  
        Object[] nodes = new Object[size];  
        int[] weights = new int[size];  
        int index = 0;  
        int weightAdder = 0;  
        for (Map.Entry<T, Integer> each : weightMap.entrySet()) {  
            nodes[index] = each.getKey();  
            weights[index++] = (weightAdder = weightAdder + each.getValue());  
        }  
        return new WeightMeta<T>((T[]) nodes, weights);  
    }  
}