Warrior's Quest

import java.util.Scanner;

public class WarriorQuest {

    private static String replaceLetter(String letter, String skill, int index) {
        char newLetter = letter.charAt(0);
        StringBuilder result = new StringBuilder();
        for (int i = 0; i < skill.length(); i++) {
            if (index == i) {
                result.append(newLetter);
                i++;
            }
            result.append(skill.charAt(i));
        }
        return result.toString();
    }

    private static String subtract(String skill, String substring, String secondSubtracting) {
        if (skill.contains(substring)) {
            skill = skill.replace(substring, secondSubtracting);
        }
        return skill;
    }

    private static String remove(String skill, String subtracting) {
        if (skill.contains(subtracting)) {
            skill = skill.replace(subtracting, "");
        }
        return skill;
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String skill = sc.nextLine();

        String input = sc.nextLine();
        while (!input.equals("For Azeroth")) {
            String[] command = input.split("\\s+");
            switch (command[0]) {
                case "GladiatorStance": {
                    skill = skill.toUpperCase();
                    System.out.println(skill);
                }
                break;
                case "DefensiveStance": {
                    skill = skill.toLowerCase();
                    System.out.println(skill);
                }
                break;
                case "Dispel": {
                    int index = Integer.parseInt(command[1]);
                    String letter = command[2];
                    if (index >= 0 && index < skill.length()) {
                        skill = replaceLetter(letter, skill, index);
                        System.out.println("Success!");
                    } else {
                        System.out.println("Dispel too weak.");
                    }
                }
                break;
                case "Target": {
                    if (command[1].equalsIgnoreCase("Change")) {
                        String substring = command[2];
                        String secondSubtracting = command[3];
                        skill = subtract(skill, substring, secondSubtracting);
                        System.out.println(skill);
                    } else if (command[1].equalsIgnoreCase("Remove")) {
                        String subtracting = command[2];
                        skill = remove(skill, subtracting);
                        System.out.println(skill);
                    }
                }
                break;
                default:
                    System.out.println("Command doesn't exist!");
                    break;
            }
            input = sc.nextLine();
        }

    }
}