Regex to convert set of small letters to capital letters in a String

Question

Could someone please tell me how do I write a Regular expression which replaces all the "aeiou" chars found in my string to capital letters like "AEIOU" and vice versa?

I wanted to use replaceAll method of java String class but not sure about the regEx.

It seems you should use `Pattern.compile` https://stackoverflow.com/questions/2770967/use-java-and-regex-to-convert-casing-in-a-string. `/[aeiou]/g` is the regex you want https://regex101.com/ — David Alvarez, Apr 30 '19 at 15:48
May be you find [that answer](https://stackoverflow.com/questions/7457886/is-there-a-way-to-use-tr-or-equivalent-in-java) useful. — Frank Neblung, Apr 30 '19 at 15:49

score 1 · Answer 1 · answered Apr 30 '19 at 17:45

This could be the solution.

It seems to me that it has to have Java 9 to use replaceAll method. Read this Use Java and RegEx to convert casing in a string

public class Main {
public static final String EXAMPLE_TEST = "This is my small example string which     I'm going to use for pattern matching.";

public static void main(String[] args)  {

    char [] chars = EXAMPLE_TEST.toCharArray(); // trasform your string in a    char array
    Pattern pattern = Pattern.compile("[aeiou]"); // compile your pattern
    Matcher matcher = pattern.matcher(EXAMPLE_TEST); // create a matcher
    while (matcher.find()) {
        int index = matcher.start(); //index where match exist
        chars[index] =  Character.toUpperCase(chars[index]); // change char array where match

    }
        String s = new String(chars); // obtain your new string :-)
    //ThIs Is my smAll ExAmplE strIng whIch I'm gOIng tO UsE fOr pAttErn mAtchIng.
    System.out.println(s);
}
}

score 0 · Answer 2 · answered Apr 30 '19 at 15:41

You can use the Pattern and Matcher class, I wrote a quick code it should be clear (subtracting 32 from an ascii alphabetical lower case char will give you its upper case, see the ascii table).

    String s = "Anthony";
    Pattern pattern = Pattern.compile("[aeiou]");
    Matcher matcher = pattern.matcher(s);
    String modifiedString = "";
    while(matcher.find())
    {
        modifiedString = s.substring(0, matcher.start()) + (char)(s.charAt(matcher.start()) - 32) + s.substring(matcher.end());
    }
    System.out.println(modifiedString);

Regex to convert set of small letters to capital letters in a String

2 Answers2