Question

I’m doing this small HW problem for class. The point of my program is to count all the blank characters in a phrase from user input. Every thing is fine until I reach my for loop. I’ve put a break point at the loop and it runs fines and counts the blank character. But when the loop ends the program crashed and gives me this error:

Exception in thread “main” java.lang.StringIndexOutOfBoundsException: String index out of range: 5

I don’t quite understand if someone could point me in the right direction.

import java.util.Scanner;
public class Cray {
    public static void main(String[] args){
              String phrase;    // a string of characters
              int countBlank;   // the number of blanks (spaces) in the phrase 
              int length;       // the length of the phrase
              char ch;          // an individual character in the string

            Scanner scan = new Scanner(System.in);

              // Print a program header
              System.out.println ();
              System.out.println ("Character Counter");
              System.out.println ();

              // Read in a string and find its length
              System.out.print ("Enter a sentence or phrase: ");
              phrase = scan.nextLine();
              length = phrase.length();

              // Initialize counts
              countBlank = 0;

              // a for loop to go through the string character by character
              // and count the blank spaces

              for(int i =0; i<=length; i++ ){
                  if(phrase.charAt(i)==' '){
                      countBlank++;

              }
              }


              // Print the results
              System.out.println ();
              System.out.println ("Number of blank spaces: " + countBlank);
              System.out.println ();
            }
        }

Answer 1

To elaborate and explain the answers given a bit:

The condition for your loop:

for(int i =0; i<=length; i++ )

Instructs the program to do the following:

1. Take an array with ‘length’ items, and start at its 0th element.
2. Process the 0th element
3. Move on to the next, ith element, and process that as well.
4. Keep doing step #3 until you reach the element at index = length

The array that you are iterating over, by definition, will have to fail at step #4. Since arrays are indexed starting at 0, an array with ‘n’ elements will have a maximum index of ‘n-1’.