Hogwarts

import java.util.Scanner;

public class Hogwarts {

    private static boolean isValid(int index, String spell) {
        return (index >= 0 && index < spell.length());
    }

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

        String spell = scanner.nextLine();

        String input = scanner.nextLine();
        while (!input.equals("Abracadabra")) {
            String[] data = input.split(" ");
            String command = data[0];

            switch (command) {
                case "Abjuration":
                    spell = spell.toUpperCase();
                    System.out.println(spell);
                    break;
                case "Necromancy":
                    spell = spell.toLowerCase();
                    System.out.println(spell);
                    break;
                case "Illusion":
                    int index = Integer.parseInt(data[1]);
                    char letter = data[2].charAt(0);

                    if (isValid(index, spell)) {
                        char[] spellArrayChar = spell.toCharArray();
                        spellArrayChar[index] = letter;
                        spell = String.valueOf(spellArrayChar);
                        System.out.println("Done!");
                    } else {
                        System.out.println("The spell was too weak.");
                    }
                    break;
                case "Divination":
                    String firstSubstring = data[1];
                    String secondSubstring = data[2];

                    spell = spell.replaceAll(firstSubstring, secondSubstring);
                    System.out.println(spell);
                    break;
                case "Alteration":
                    String subString = data[1];
                    spell = spell.replaceAll(subString, "");
                    System.out.println(spell);
                    break;
                default:
                    System.out.println("The spell did not work!");
            }
            input = scanner.nextLine();
        }
    }
}