Swap positions of the first appearance of letter 'a' with the last appearance of letter 'o' Java

artshakhov :

The task is asking me to make from the String, for example "aaligatoor", output like: "oaligatoar" I found a solution like:

public static String letterReplacement(final String word) {
            String o = "o";
            String a = "a";
            if (word.contains("a") && word.contains("o")) {
                return word.replaceFirst("a", "o")
                           .replaceFirst("(?s)(.*)" + 'o', "$1" + 'a');
            } else {
                return "Your word does not contain both of 'a' and 'o' letters, sorry...";
            }
        }

but it looks tricky, maybe someone knows any more understandable ways to solve this? I appreciate your assistance and attention very much.

Shar1er80 :

Find the first index of the "a" (String.indexOf()) and the last index of "o" (String.lastIndexOf()). If both indexes are > -1 then swap the letters

Something like:

public class StackOverflow {
    public static void main(String[] args) {
        String data = "aaligatoor";

        int firstAindex = data.indexOf("a");
        int lastOindex = data.lastIndexOf("o");

        if (firstAindex > -1 && lastOindex > -1) {
            char[] letters = data.toCharArray();
            letters[firstAindex] = 'o';
            letters[lastOindex] = 'a';

            data = new String(letters);
        }
        System.out.println(data);
    }
}

Result

oaligatoar