How would I capitialize the first letter of a sentence in Java?

Question

I tried splitting up the words in the line and checking if they had periods, but I got an error:

falls.falls.falls.Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 6
at Alpha.main(Alpha.java:10)

Code:

import java.io.*;
import java.util.*;

public class Alpha
{
    public static void main(String[] args)
    {
        String phrase = "the moon falls. the flowers grew.";
        String beta = "";
        String[] array = phrase.split(" ");
        for (int i = 0; i < array.length; i++)
        {
            if (array[i].endsWith("."))
            {
                array[i + 1] = array[i + 1].substring(0, 1).toUpperCase() + array[i + 1].substring(1);

                beta = beta + array[i];
            }
            System.out.print(beta);
        }
    }
}

(Also I don't think that's how I would call another word of an array, any suggestions on how I can fix that?)

Imagine what will happen in your code when it reaches the terminal period to see why you're getting that exception (hint `array[i + 1]` will do what when this happens?). Why not simply iterate through the String one character at a time? — Hovercraft Full Of Eels, Nov 18 '12 at 04:08

score 1 · Answer 1 · answered Nov 18 '12 at 04:13

1

You are not handling the case where your input ends with .. Also, general sentences may have a space after . before the next sentence follows. You should consider that too. Also, you may want to look at this version of indexOf that takes a fromIndex.

answered Nov 18 '12 at 04:13

Vikdor

23,934
10
61
84

score 0 · Answer 2 · answered Nov 18 '12 at 04:11

0

I would suggest using split() on ".". That way, you could then check if there were a character following the period, and then capitalize it.

answered Nov 18 '12 at 04:11

awolfe91

1,627
1
11
11

score 0 · Answer 3 · edited May 23 '17 at 12:27

0

Based on the code of the question Regular expression match a sentence

import java.util.regex.*;
public class TEST {
    public static void main(String[] args) {
        String subjectString = 
        "This is a sentence. " +
        "So is \"this\"! And is \"this?\" " +
        "This is 'stackoverflow.com!' " +
        "Hello World";
        String[] sentences = null;
        Pattern re = Pattern.compile(
            "# Match a sentence ending in punctuation or EOS.\n" +
            "[^.!?\\s]    # First char is non-punct, non-ws\n" +
            "[^.!?]*      # Greedily consume up to punctuation.\n" +
            "(?:          # Group for unrolling the loop.\n" +
            "  [.!?]      # (special) inner punctuation ok if\n" +
            "  (?!['\"]?\\s|$)  # not followed by ws or EOS.\n" +
            "  [^.!?]*    # Greedily consume up to punctuation.\n" +
            ")*           # Zero or more (special normal*)\n" +
            "[.!?]?       # Optional ending punctuation.\n" +
            "['\"]?       # Optional closing quote.\n" +
            "(?=\\s|$)", 
            Pattern.MULTILINE | Pattern.COMMENTS);
        Matcher reMatcher = re.matcher(subjectString);
        while (reMatcher.find()) {
            String sentence = reMatcher.group();
            sentence = sentence.substring(0,1).toUpperCase() + sentence.substring(1);
            System.out.println(sentence);
        } 
    }
}

edited May 23 '17 at 12:27

Community

1
1

answered Nov 18 '12 at 04:14

Alexandre Lavoie

8,711
3
31
72

This is overkill to the nth degree. I suppose you would also suggest that one hunts sparrows with surface to air missiles? – Hovercraft Full Of Eels Nov 18 '12 at 04:22
You can't say if it is overkill or not since you don't know the complete application of the user, he will judge by himself. This answer is a suggestion, not an obligation. – Alexandre Lavoie Nov 18 '12 at 04:26
come on now. The OP doesn't even know how to use arrays properly and you're suggesting that regular expressions be suggested to him? Please delete this answer as it will not help him, I can assure you. – Hovercraft Full Of Eels Nov 18 '12 at 04:28
1

This answer can be perfect for someone else that find his question. If you are not happy I'm sorry for you. – Alexandre Lavoie Nov 18 '12 at 04:31
Edited to allow me to remove my down-vote, but I still stand by my comments above. – Hovercraft Full Of Eels Nov 18 '12 at 04:37

score 0 · Answer 4 · answered Nov 18 '12 at 04:31

Consider this:

    String phrase = "the moon falls. the flowers grew.";
    char[] a = phrase.toCharArray();
    boolean f = true;
    for (int i = 0; i < a.length; i++) {
        if (f) {
            if (a[i] != ' ') {
                a[i] = Character.toUpperCase(a[i]);
                f = false;
            }
        } else if (a[i] == '.') {
            f = true;
        }
    }
    phrase = new String(a);
    System.out.println(phrase);

How would I capitialize the first letter of a sentence in Java?

4 Answers4