Java基于余弦方法实现的计算相似度算法示例

import java.util.HashMap;import java.util.Iterator;import java.util.Map;public class SimilarDegreeByCos{  /*   * 计算两个字符串(英文字符)的相似度，简单的余弦计算，未添权重   */   public static double getSimilarDegree(String str1, String str2)   {    //创建向量空间模型，使用map实现，主键为词项，值为长度为2的数组，存放着对应词项在字符串中的出现次数     Map<String, int[]> vectorSpace = new HashMap<String, int[]>();     int[] itemCountArray = null;//为了避免频繁产生局部变量，所以将itemCountArray声明在此     //以空格为分隔符，分解字符串     String strArray[] = str1.split(" ");     for(int i=0; i<strArray.length; ++i)     {       if(vectorSpace.containsKey(strArray[i]))         ++(vectorSpace.get(strArray[i])[0]);       else       {         itemCountArray = new int[2];         itemCountArray[0] = 1;         itemCountArray[1] = 0;         vectorSpace.put(strArray[i], itemCountArray);       }     }     strArray = str2.split(" ");     for(int i=0; i<strArray.length; ++i)     {       if(vectorSpace.containsKey(strArray[i]))         ++(vectorSpace.get(strArray[i])[1]);       else       {         itemCountArray = new int[2];         itemCountArray[0] = 0;         itemCountArray[1] = 1;         vectorSpace.put(strArray[i], itemCountArray);       }     }     //计算相似度     double vector1Modulo = 0.00;//向量1的模     double vector2Modulo = 0.00;//向量2的模     double vectorProduct = 0.00; //向量积     Iterator iter = vectorSpace.entrySet().iterator();     while(iter.hasNext())     {       Map.Entry entry = (Map.Entry)iter.next();       itemCountArray = (int[])entry.getValue();       vector1Modulo += itemCountArray[0]*itemCountArray[0];       vector2Modulo += itemCountArray[1]*itemCountArray[1];       vectorProduct += itemCountArray[0]*itemCountArray[1];     }     vector1Modulo = Math.sqrt(vector1Modulo);     vector2Modulo = Math.sqrt(vector2Modulo);     //返回相似度    return (vectorProduct/(vector1Modulo*vector2Modulo));   }   /*   *   */   public static void main(String args[])   {     String str1 = "gold silver truck";     String str2 = "Shipment of gold damaged in a fire";     String str3 = "Delivery of silver arrived in a silver truck";     String str4 = "Shipment of gold arrived in a truck";     String str5 = "gold gold gold gold gold gold";     System.out.println(SimilarDegreeByCos.getSimilarDegree(str1, str2));     System.out.println(SimilarDegreeByCos.getSimilarDegree(str1, str3));     System.out.println(SimilarDegreeByCos.getSimilarDegree(str1, str4));     System.out.println(SimilarDegreeByCos.getSimilarDegree(str1, str5));   }}