Trying to use an indexOf position in order to capitalize a letter in a string

Question

Edit:

I've tried to compile all of the code into a single program. Now all I need is to figure out how to return the modified string from the method. What do I have to put in order to achieve this?

Here's the new code:

        public class String_Fixer {

            public static void main(String[] args) {

                String userInput, newString;
                Scanner keyboard = new Scanner(System.in);
                System.out.println("This program takes sentences and capitalizes them for you.");
                System.out.println("Please write a few sentences.");
                System.out.println("");
                userInput = keyboard.nextLine();
                System.out.println("");


                System.out.println("Here is the original sentence:");
                System.out.println(userInput);
                System.out.println("");
                System.out.println("And here is the modified sentence:");
                System.out.println();  
            }

            public static List<Integer> stringFixer(String userInput) {
                List<Integer> indexes = new ArrayList<>();
                int first = 0, offset = 2, index, offset_index;
                while ((index = userInput.indexOf('.', first)) != -1) {
                    offset_index = index + offset;
                    if (offset_index < userInput.length()) {
                        indexes.add(offset_index);
                    }
                    first = index + 1;
                }
                while ((index = userInput.indexOf('?', first)) != -1) {
                    offset_index = index + offset;
                    if (offset_index < userInput.length()) {
                        indexes.add(offset_index);
                    }
                    first = index + 1;
                }
                return indexes;
            }

            public static String CapatilizeChars(List<Integer> indexes, String string) {
                StringBuilder newString = new StringBuilder(string);
                for (int i : indexes) {
                    char capChar = Character.toUpperCase(newString.charAt(i));
                    newString.setCharAt(i, capChar);
                }
                return newString.toString();
            }

        }

Answer 1

Use the Character.toUpperCase(CHARACTER); method to get the upper case variant of a character.

See this post: Indexes of all occurrences of character in a string for information on finding all indexes of a character in a String.

EDIT:

Here's how I would tackle the problem. First get the indexes that need to be changed using this method:

public static List<Integer> getIndexesOf(String regex, String stringToCheck, int offset) {

    List<Integer> indexes = new ArrayList<>();

    // Where to begin each indexof operation
    int first = 0;

    // The direct indexof result
    int index;
    // The indexof result offset by the specified amount
    int offset_index;

    // While we are still getting results from index of, save result under index and loop
    while ((index = stringToCheck.indexOf(regex, first)) != -1) {

        offset_index = index + offset;

        // If the offset index doesn't excede the strings length add it to list
        if (offset_index < stringToCheck.length()) {

            indexes.add(offset_index);

        }

        first = index + 1;

    }

    return indexes;

}

Then capitalize each index using this method:

public static String CapatilizeChars(List<Integer> indexes, String string) {

    StringBuilder newString = new StringBuilder(string);

    // For each index capatilize the specified char
    for (int i : indexes) {

        char capChar = Character.toUpperCase(newString.charAt(i));

        newString.setCharAt(i, capChar);

    }

    return newString.toString();

}

This isn't the fastest way of doing it, but it has the benefit of the method being more useful then a specific capitalize_char_after_regex method. You could easily combine this into one method by taking the code within the for loop of the second method and putting it into the first.

EDIT 2:

Fix for your updated code:

Replace: StringFixer modifiedString = new StringFixer();

With: String modifiedString = StringFixer.CapatilizeChars(StringFixer.getIndexesOf(userInput), userInput);

And remove the regex parameter from the getIndexesOf method since you aren't using them in your application.

The methods I gave you are static, which means they are not associated with an instance of an object. In other words, you don't need to construct the StringFixer class to use them.