CODEWITHSUNDEEP
javastringexception
Jack
Jack

Reputation: 3

String index out of range: -1; substring issue

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.

Upvotes: 0

Views: 4667

Answers (4)

Jamie
Jamie

Reputation: 511

My solution does not check for words that are not actually words,

import java.util.Scanner;

public class SentenceWordCount {
    Scanner s = new Scanner (System.in);
    int wordCount;

    public SentenceWordCount() {
        System.out.println("Enter a sentence");

        String sentenceEntered = s.nextLine();
        String[] brokenSentence = sentenceEntered.split(" ");

        wordCount = brokenSentence.length;

        if(wordCount > 3){
        for(String s : brokenSentence){
                System.out.println(s);
            }
        }

        System.out.println("Number of words equals : " + wordCount);
    }
}

Cheers,

Jamie

Upvotes: 0

PermGenError
PermGenError

Reputation: 46438

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);

Upvotes: 1

Hovercraft Full Of Eels
Hovercraft Full Of Eels

Reputation: 285450

  • Myself, I'd use String#split(...) method and would be able to solve this in just a few lines of code.
  • But if you must do it this way, don't do a for loop or loop charCount number of times since charCount is the size of the String and you certainly don't want to loop this many times. It just doesn't make sense. Rather, you want to loop the number of spaces, not the number of characters, which brings me to the next recommendation:
  • Use a while loop, not a for loop and loop until -1 is returned by the indexOf(...) method. In other words, let Java do the hard work of figuring out when the String has run out of spaces rather than you guess.

Upvotes: 0

Reimeus
Reimeus

Reputation: 159874

You need to check that the index of space here. String.indexOf() will return -1 if the search string is not found.

int space = sentence.indexOf(" ");
int endSpace = space + 1;
if (space != -1) {
    sentence = sentence.substring(0, space) + "\n"
            + sentence.substring(endSpace, sentence.length());
}

Upvotes: 2

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