Programming Forums > Application Development > Java

FidI · Nov 10th, 2004, 10:43 PM

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....

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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());
  	
             

            }
        }



    }
}

drunkenCoder · Nov 18th, 2004, 6:01 AM

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....

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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

eccles · Nov 21st, 2004, 7:00 PM

Quote:

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

alternatively, just recast it to a string:

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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.

Nov 10th, 2004, 10:43 PM	#1
FidI Newbie Join Date: Nov 2004 Posts: 7 Rep Power: 0	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.... (Toggle Plain Text) 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()); } } } } 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()); } } } }

Nov 18th, 2004, 6:01 AM	#2
drunkenCoder Newbie Join Date: Nov 2004 Posts: 8 Rep Power: 0	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.... (Toggle Plain Text) 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] ); } } } 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

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Programming Forums > Application Development > Java

Problem With "valueof"