Question

I’m writing a program for class which counts words in a string and, if the inputted string has more than 3 words, prints the sentence again, but with each word on its own line.

So I’m trying to replace spaces with \n. When I input a sentence that has more than 3 words, I get:

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: -1
        at java.lang.String.substring(String.java:1937)
        at lab3.main(lab3.java:32)

Here’s my code:

import java.util.Scanner;

public class lab3 {

public static void main(String [] args) {

    Scanner scan = new Scanner (System.in);

    int wordCount = 1;
    char aChar;

    System.out.println("Enter a sentence.");

    String sentence = scan.nextLine();
    int charCount = sentence.length();

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

                    continue;
            } else {
                    wordCount++;
                    }
            }

    System.out.println("Number of words = " + wordCount);

            if (wordCount >= 4){
            for (int i = 0; i <= charCount; i++){
                    int space = sentence.indexOf(" ");
                    int endSpace = space + 1;
                    sentence = sentence.substring(0, space) 
                            + "\n"
                            + sentence.substring(endSpace, sentence.length());
                    }
                    System.out.println(sentence);

            } else {
            System.out.println(sentence);

            }

    }
}

The problem seems to be coming from the for loop at line 31, but I don’t understand how it’s returning -1 when I input a sentence longer than 3 words. Am I using substring wrong?
Any help would be appreciated.

Answer 1

If you want to keep your code then you would have to do a check when doing sentence.index(” “) if it return -1. if it returns you breakout of the loop as below.
however, this isnt a good style of coding. i’d rather do with regex or other simpler methods from String API.

 if (wordCount >= 4){
            for (int i = 0; i <charCount-3; i++){
                    int space = sentence.indexOf(" ");
                    if(space==-1){// check if space is -1
                        break;
                    }   
                    System.out.println(i+ " " + space);
                    int endSpace = space + 1;
                    sentence = sentence.substring(0, space)
                            + "\n"
                         + sentence.substring(endSpace, sentence.length()-1);
                    }
                    System.out.println(sentence);