Programming Forums - Problem With "valueof"

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for one more time here i am........ sorry guys....... :(
this time i am trying to create a java file that reads lines and adds each line to an array...here is the code...it compiles but i am getting an error message: exception in thread "main" java.lang.ArrayIndexOutOfBoundsException....:(

import java.io.*;

import java.util.*;



public class token4

{

    public static void main(String args[]) throws IOException{

        String question;

        StringTokenizer currentString;

  //open file

        BufferedReader InputData = new BufferedReader(new FileReader("./inputData.txt"));



  int i = 0;

  //read each line

        while ((question = InputData.readLine()) != null){

          //new string array

    String[] LineString = new String[i];

   i++;

            currentString = new StringTokenizer(question,".");

               



          while (currentString.hasMoreElements()) {

          //add Strings to array...

          LineString[i] = String.valueOf(currentString.nextElement());

          

             



            }

        }







    }

}

You are declaring a String array of zero length in the first pass of your first while loop. That is a String array with one element otherwise known as just a plain String (no array). In the second while loop, you are indexing your "array" past its length (which is ONE). Hence the java.lang.ArrayIndexOutOfBoundsException.

Try it with a Vector....

import java.io.*;

import java.util.*;



public class token4

{

   public static void main(String args[]) throws IOException

   {

       String question;

       StringTokenizer currentString;

       //use a Vector since you don't know how many sentences the file 

       //will be

       Vector v = new Vector();

       String temp;

       int i = 0;

       //i changed the path of the file

       FileReader file = new FileReader("C:/inputData.txt");

       BufferedReader InputData = new BufferedReader( file );

       //read each line of the file

       while ((question = InputData.readLine()) != null)

       {

          currentString = new StringTokenizer(question,".");

          while (currentString.hasMoreElements()) 

          {

            //store sentences in temporary string

            temp = String.valueOf(currentString.nextElement());

            //add the string to the Vector

            v.addElement( temp );

            //print statement for debugging

            //System.out.println(v.elementAt( i ));

            //i++;

          }

       }

       //if you need the data in string arrays, the portion of code below

       //does this for you

       //declare String array for length of vector

       String[] LineString = new String[v.size()];

       //iterate through the vector, putting each element into an index

       //of "LineString"

       for (int bob = 0; bob < v.size(); bob++ )

       {

         LineString[bob] = v.elementAt( bob ).toString();

         //print statement for debugging

         //System.out.println( LineString[bob] );

       }

   

   }

}

Hope this helps

Quote:

LineString[bob] = v.elementAt( bob ).toString();

alternatively, just recast it to a string:

LineString[bob] = (String)v.elementAt( bob );

since you already know that the vector contains strings (albeit ones that have had their cast widened to Object) - probably best to get into the habit of using casting in a situation like this, rather than calling methods on the elements as you retrieve them - because one day, in some situation or another - that won't work, and you'll be left wondering what to do... (eg if you are storing instances of an object you created yourself, will you start writing a 'toMyObject()' method? hehe you wouldn't want to go there ;)

This is not a criticism of drunkenCoder's example - its just best if you know the other method as well - especially when you start storing other data types in vectors (or any other type of collection for that matter) and you don't have a method that does the casting for you... - like .toString(), or Double.parseDouble()...

so yeah - remember - you don't need a method to recast an object as you remove it from a collection - just a cast. :)