Secret Chat

import java.util.Scanner;

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

        String string = scanner.nextLine();
        String input = scanner.nextLine();

        while (!"Reveal".equals(input)) {
            String[] tokens = input.split(":\\|:");
            String command = tokens[0];

            switch (command) {
                case "InsertSpace":
                    int index = Integer.parseInt(tokens[1]);
                    String sub1 = string.substring(0, index);
                    String sub2 = string.substring(index);
                    string = sub1 + " " + sub2;
                    System.out.println(string);
                    break;
                case "Reverse":
                    String substring = tokens[1];

                    if (string.contains(substring)) {
                        StringBuilder sb = new StringBuilder();
                        for (int i = 0; i < substring.length(); i++) {
                            sb.append(substring.charAt(i));
                        }
                        sb.reverse();
                        string = string.replaceFirst("[\\W][\\w]+", sb.toString());
                        System.out.println(string);
                    } else {
                        System.out.println("error");
                    }
                    break;
                case "ChangeAll":
                    string = string.replace(tokens[1], tokens[2]);
                    System.out.println(string);
                    break;
            }

            input = scanner.nextLine();
        }
        System.out.println(String.format("You have a new text message: %s", string));
    }
}