I keep getting a java.lang.arrayindexoutofboundsexception 5 error, but I can't find the error

Question

*Heads up this is technically HOMEWORK , but it won't let me add the tag for some reason

the compiler seems to be specifically pointing to the specialPrintData() method, but I honestly can't figure out what's wrong. This is the last step to finishing my program so all help is welcomed!

import java.util.Scanner;
import java.io.File;

public class Lab07
{
   static final int MAX = 100;  // global constant

   static public int readFile( String [ ] fd, String fileName)  throws Exception
   {

   File f = new File( fileName );
   Scanner input = new Scanner( f );

   int count = 0;

   while( count < fd.length && input.hasNextLine( ) )
   {
       fd[count] = input.nextLine( );
       count++;
   }

   if (input.hasNext( ) )
   {
      System.out.println("File is larger than array. Program is terminating.");
      System.exit(0);
   }

   else
   {
      System.out.println("Read " + count + " int values from file.");
   }
   input.close( );

   return count;
}   

static public void printData( String [ ] fd, int count )
{
  for( int i = 0; i < count; i++)
  {
    System.out.println(  fd[i] );
  }
  System.out.println();
}

static public void specialPrintData( String [ ] fd, int count )
{
  for( int i = 3; i < count; i++)
  {
    System.out.printf(" %4s ", fd[i] );
  }
}

static public int countWords(String str)
{
    int count = 1;
    for (int i = 0; i <= str.length() - 1; i++)
    {
        if (str.charAt(i) == ' ' && str.charAt(i+1) != ' ')
        {
            count++;
        }
    }
    return count;
}

static public void printNicelyFormattedData( String [ ] fd, int count )
{
    int numKids = 0;

    for( int i = 0; i < count; i++)
    {   
        if (countWords( fd[i] ) > 2)
        {
            numKids = ((countWords( fd[i]) - 3));
        }

        String [ ] list1 = fd[i].split(" ");

        System.out.println( list1[0] + " and " + list1[1] + " " + list1[2] + " have " + numKids + " children:" + "\n");

        specialPrintData( list1, count);
    }

    System.out.println();
}


   static public void main( String args [ ] )  throws Exception
   {
    if( args.length < 1 )
    {
       System.out.println("Error running program!");
       System.out.println("Usage:  java Lab07   L7d.txt");
       System.exit( 0 );
    }

    String [ ] fileData = new String[MAX];
    int count = 0;

    count = readFile( fileData, args[0] );
    System.out.println( "Array of file data contains " + count + " lines of data:");
    printData( fileData, count );

    System.out.println("*******************************************************");
    System.out.println("Family Data for past and present presidential families:");
    printNicelyFormattedData( fileData, count );

}
}

Answer 1

In the countWords method you are accessing the character at index i + 1 . Therefore you must check before like this:

if (i + 1 < str.length()) {

When you have fixed this problem, you will get a NullPointerException . Looking at the stack trace, you can see in which line of the code it occurred.

To fix that, you should replace the String[] with an ArrayList<String> . Then you can get rid off the MAX constant, since a list is like an array, but it grows automatically whenever you add something to it.

Answer 2

the problem is in your printNicelyFormattedData method. At this line

specialPrintData( list1, count);

you are passing the count of the String[] fd and not the count of String[] list .

that is instead of the number of words in a line, you are passing the number of lines in the file.

so instead of that, use this

specialPrintData( list1, list1.length);

EDIT:

as @Roland mentioned there is another exception likely to happen but only in the below case.

StringIndexOutOfBoundsException is likely to happen at this line if (str.charAt(i) == ' ' && str.charAt(i+1) != ' ') only if the last character of the line is ' ' otherwise the first condition would fail for the last character and the second condition would never be checked

hope this helps.