Validation_using_regex.java

package Assignment_2;

import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Validation_using_regex {

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        int choice;

        do {
            System.out.println("\n--- REGEX VALIDATION MENU ---");
            System.out.println("1. Validate Mobile Number");
            System.out.println("2. Validate Email ID");
            System.out.println("3. Validate Username");
            System.out.println("4. Validate Password");
            System.out.println("5. Exit");

            try {
                choice = sc.nextInt();
                sc.nextLine(); // consume newline

                switch (choice) {

                    case 1: {
                        System.out.println("Enter Mobile Number:");
                        String Mobilenum = sc.nextLine();

                        Pattern p = Pattern.compile("^[6-9][0-9]{9}$");
                        Matcher m = p.matcher(Mobilenum);

                        if (m.matches()) {
                            System.out.println("Welcome! Mobile Number is Valid");
                        } else {
                            System.out.println("Invalid Mobile Number");
                        }
                        break;
                    }

                    case 2: {
                        System.out.println("Enter Email ID:");
                        String email = sc.nextLine();

                        Pattern p = Pattern.compile("^[A-Za-z0-9+_.-]+@[A-Za-z0-9.-]+$");
                        Matcher m = p.matcher(email);

                        if (m.matches()) {
                            System.out.println("Welcome! Email ID is Valid");
                        } else {
                            System.out.println("Invalid Email ID");
                        }
                        break;
                    }

                    case 3: {
                        System.out.println("Enter Username:");
                        String username = sc.nextLine();

                        Pattern p = Pattern.compile("^[A-Za-z][A-Za-z0-9_]{4,14}$");
                        Matcher m = p.matcher(username);

                        if (m.matches()) {
                            System.out.println("Welcome! Username is Valid");
                        } else {
                            System.out.println("Invalid Username");
                        }
                        break;
                    }

                    case 4: {
                        System.out.println("Enter Password:");
                        String password = sc.nextLine();

                        Pattern p = Pattern.compile("^(?=.*[A-Z])(?=.*[a-z])(?=.*\\d)(?=.*[@#$%]).{8,}$");
                        Matcher m = p.matcher(password);

                        if (m.matches()) {
                            System.out.println("Welcome! Password is Strong");
                        } else {
                            System.out.println("Invalid Password");
                        }
                        break;
                    }

                    case 5:
                        System.out.println("Exiting Program...");
                        break;

                    default:
                        System.out.println("Invalid Choice");
                }

            } catch (Exception e) {
                System.out.println("Error: Invalid Input");
                sc.nextLine(); // clear buffer
                choice = 0;
            }

        } while (choice != 5);

        sc.close();
    }
}