Email Validator

import java.util.ArrayList;
import java.util.Scanner;

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

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

        while (!"Complete".equals(input)) {
            String[] tokens = input.split("\\s+");
            String command = tokens[0];

            switch (command) {
                case "Make":
                    if (tokens[1].equals("Upper")) {
                        string = string.toUpperCase();
                    } else {
                        string = string.toLowerCase();
                    }
                    System.out.println(string);
                    break;
                case "GetDomain":
                    String newString = string.substring(string.length() - 3);
                    System.out.println(newString);
                    break;
                case "GetUsername":
                    if (!string.contains("@")) {
                        System.out.println(String.format("The email %s doesn't contain the @ symbol.", string));
                    } else {
                        int symbol = string.indexOf('@');
                        String text = string.substring(0, symbol);
                        System.out.println(text);
                    }
                    break;
                case "Replace":
                    string = string.replace(tokens[1], "-");
                    System.out.println(string);
                    break;
                case "Encrypt":
                    ArrayList<String> encrypt = new ArrayList<>();

                    for (int i = 0; i < string.length(); i++) {
                        int num = string.charAt(i);
                        encrypt.add(String.valueOf(num));
                    }
                    System.out.println(String.join(" ", encrypt));
                    break;
            }

            input = scanner.nextLine();
        }
    }
}