Validating e-mail username and password using try/catch block

Question

I'm trying to write a code that validates an email as a username and a password that has at least one uppercase, one lowercase, and one special character. When I run the program, I'm getting "Successfully signed up." no matter what I input. I believe my error is in my try/catch block.

    import java.util.Scanner;

    public class UserSignUp {
        public static void main(String[] args) {
            Scanner input1 = new Scanner(System.in);
            Scanner input2 = new Scanner(System.in);
            String username;
            String password;

        try {
            System.out.print("Enter your username: ");
            username = input1.nextLine();
            System.out.print("Enter your password: ");
            password = input2.nextLine();
        }
        catch (IllegalArgumentException e) {
            System.out.println(e);
        }
        System.out.println("Successfully signed up.");
    }

    public static void validateUsername(String username) throws IllegalArgumentException {
        String pattern = ".+@.+\\.com";
        if (username.matches(pattern)) {
            throw new IllegalArgumentException("Invalid username.");
        }
    }

    public static void validatePassword(String password) throws IllegalArgumentException {
        boolean isUppercase = false;
        boolean isLowercase = false;
        boolean isDigit = false;
        boolean hasSpecialCharacter = false;
        char ch = 0;

        for (int i = 0; i < password.length(); i++) {
            ch = password.charAt(i);
            if (Character.isUpperCase(ch)) {
                isUppercase = true;
            } else {
                throw new IllegalArgumentException("Password must contain an uppercase letter.");
            }
            if (Character.isLowerCase(ch)) {
                isLowercase = true;
            } else {
                throw new IllegalArgumentException("Password must contain a lowercase letter.");
            }
            if (Character.isDigit(ch)) {
                isDigit = true;
            } else {
                throw new IllegalArgumentException("Password must contain a digit.");
            }
            if (!Character.isDigit(password.charAt(ch)) && !Character.isLetter(password.charAt(ch))) {
                hasSpecialCharacter = true;
            } else {
                throw new IllegalArgumentException("Password must contain a special character.");
            }
        }
    }
}

Answer 1

Here is my solution to it, the explanation is already embedded:

import java.util.Scanner;

public class UserSignUp {
    public static void main(String[] args) {
        // No need for two scanners, one scanner can accept multiple (also
        // multiple-lined) inputs.
        Scanner in = new Scanner(System.in);

        try {
            // Put validation inside the try block.
            // Regarding there are no other use of the variables, it is unnecessary to give
            // the two variables "Method Level Scope" instead of "Block Scope".
            System.out.print("Enter your username: ");
            String username = in.nextLine();
            validateUsername(username);
            System.out.print("Enter your password: ");
            String password = in.nextLine();
            validatePassword(password);
            // Put the println() inside the try block.
            System.out.println("Successfully signed up.");
        } catch (IllegalArgumentException e) {
            System.out.println(e);
        }

    }

    public static void validateUsername(String username) throws IllegalArgumentException {
        String pattern = ".+@.+\\.com";
        // If not matches the pattern,
        if (!username.matches(pattern)) {
            throw new IllegalArgumentException("Invalid username.");
        }
    }

    public static void validatePassword(String password) throws IllegalArgumentException {
        boolean isUppercase = false;
        boolean isLowercase = false;
        boolean isDigit = false;
        boolean hasSpecialCharacter = false;
        char ch = '\0';

        for (int i = 0; i < password.length(); i++) {
            ch = password.charAt(i);
            if (Character.isUpperCase(ch))
                isUppercase = true;
            if (Character.isLowerCase(ch))
                isLowercase = true;
            if (Character.isDigit(ch))
                isDigit = true;
            // ch is already defined as a character.
            if (!Character.isDigit(ch) && !Character.isLetter(ch))
                hasSpecialCharacter = true;
        }

        // Ask for the constraints after read through all characters.
        if (isUppercase != true)
            throw new IllegalArgumentException("Password must contain an uppercase letter.");
        else if (isLowercase != true)
            // Fix the error message of lower-case letters.
            throw new IllegalArgumentException("Password must contain a lowercase letter.");
        else if (isDigit != true)
            throw new IllegalArgumentException("Password must contain a digit.");
        else if (hasSpecialCharacter != true)
            throw new IllegalArgumentException("Password must contain a special character.");

    }
}

Hope this answer helps and please leave this question as it is as someone might need it, unless there is important changes.