使用ArrayList時解決ArrayIndexOutOfBoundException

Question

我是java開發領域的初學者，仍然是Java編程的學習者。我想在NetBeans IDE上看到支持向量機分類器的輸出。所以我複製了這個附加的代碼片段，並嘗試使用所有其他所需的類和主要方法運行，但我得到Number format exception當我給一個文件包含輸入如23,25,26,27在方法調用期間loadBinaryProblem()在主要方法，如果我刪除所有的逗號，並將其替換爲空間例如：23 25 26 27然後我得到ArrayIndexOutOfBound異常，而不是它。所以任何人都可以幫助正確地獲得輸出而不會出現任何錯誤。

package svmlearn; 

import java.io.*; 
import java.util.*; 

/** 
* Class representing an optimization problem (a data setting); 
* taken from liblinear; "bias" excluded 
* @author miafranc 
* 
*/ 
public class Problem { 
     /** The number of training data */ 
     public int l; 
     /** The number of features (including the bias feature if bias >= 0) */ 
     public int n; 
     /** Array containing the target values */ 
     public int[] y; 
     /** Map of categories to allow various ID's to identify classes with. */ 
     public CategoryMap<Integer> catmap; 
     /** Array of sparse feature nodes */ 
     public FeatureNode[][] x; 
     public Problem() { 
       l = 0; 
       n = 0; 
       catmap = new CategoryMap<Integer>(); 
     } 
     /** 
     * Loads a binary problem from file, i.e. having 2 classes. 
     * @param filename The filename containing the problem in LibSVM format. 
     */ 
     public void loadBinaryProblem(String filename) { 
       String row; 
       ArrayList<Integer> classes = new ArrayList<Integer>(); 
       ArrayList<FeatureNode []> examples = new ArrayList<FeatureNode []>(); 
       try { 
         BufferedReader r = new BufferedReader(new FileReader(filename)); 
         while ((row = r.readLine()) != null) { 
           String [] elems = row.split(" "); 
           //Category: 
           Integer cat = Integer.parseInt(elems[0]); 
           catmap.addCategory(cat); 
           if (catmap.size() > 2) { 
             throw new IllegalArgumentException("only 2 classes allowed!"); 
           } 
           classes.add(catmap.getNewCategoryOf(cat)); 
           //Index/value pairs: 
           examples.add(parseRow(elems)); 
         } 
         x = new FeatureNode[examples.size()][]; 
         y = new int[examples.size()]; 
         for (int i=0; i<examples.size(); i++) { 
           x[i] = examples.get(i); 
           y[i] = 2*classes.get(i)-1; //0,1 => -1,1 
         } 
         l = examples.size(); 
       } catch (Exception e) { 
         System.out.println(e); 
       } 
     } 
     /** 
     * Parses a row from a LibSVM format file. 
     * @param row The already split row on spaces. 
     * @return The corresponding FeatureNode. 
     */ 
     public FeatureNode [] parseRow(String [] row) { 
       FeatureNode [] example = new FeatureNode[row.length-1]; 
       int maxindex = 0; 
       for (int i=1; i<row.length; i++) { 
         String [] iv = row[i].split(":"); 
         int index = Integer.parseInt(iv[0]); 
         if (index <= maxindex) { 
           throw new IllegalArgumentException("indices must be in increasing order!"); 
         } 
         maxindex = index; 
         double value = Double.parseDouble(iv[1]); 
         example[i-1] = new FeatureNode(index, value); 
       } 
       if (n < maxindex) 
         n = maxindex; 
       return example; 
     } 
} 

Answer 1

我猜NumberformatExceptions來自：

String [] elems = row.split(" "); //nothing done by "23,25,26,27" 
//Category: 
Integer cat = Integer.parseInt(elems[0]); //you are trying to parse "23,25,26,27" 

ArrayIndexOutOfBound來自：

String [] iv = row[i].split(":");//nothing done 
... 
double value = Double.parseDouble(iv[1]);//1 is out of bound