Java Program to check the validity of a Password using User Defined Exception

Password checker program basically checks if the password is valid or not based on password policies mention below:

• Password should not contain any space.
• Password should contain at least one digit(0-9).
• Password length should be between 8 to 15 characters.
• Password should contain at least one lowercase letter(a-z).
• Password should contain at least one uppercase letter(A-Z).
• Password should contain at least one special character ( @, #, %, &, !, $, etc….).

Example:

Input: GeeksForGeeks 
Output: Invalid Password!
This input contains lowercase 
as well as uppercase letters 
but does not contain digits 
and special characters.

Input: Geek007@GFG
Output: Valid Password
This input satisfies all password
policies mentioned above.

Approach:

• Create a User-defined exception named “InvalidPasswordException” as explained below.
• Then check for the validity of the password on the required parameters.
• If any parameter is not met, then throw the InvalidPasswordException.

Below is the implementation of the above approach:

// Java Program to check the validity
// of a Password using User-Defined Exception

// Class for user-defined InvalidPasswordException
class InvalidPasswordException extends Exception {

    int passwordConditionViolated = 0;

    public InvalidPasswordException(int conditionViolated)
    {
        super("Invalid Password: ");
        passwordConditionViolated = conditionViolated;
    }

    public String printMessage()
    {
        // Call constructor of parent Exception
        // according to the condition violated
        switch (passwordConditionViolated) {

        // Password length should be
        // between 8 to 15 characters
        case 1:
            return ("Password length should be"
                    + " between 8 to 15 characters");

        // Password should not contain any space
        case 2:
            return ("Password should not"
                    + " contain any space");

        // Password should contain// at least one digit(0-9)
        case 3:
            return ("Password should contain"
                    + " at least one digit(0-9)");

        // Password should contain at least
        // one special character ( @, #, %, &, !, $ )
        case 4:
            return ("Password should contain at "
                    + "least one special character");

        // Password should contain at least
        // one uppercase letter(A-Z)
        case 5:
            return ("Password should contain at"
                    + " least one uppercase letter(A-Z)");

        // Password should contain at least
        // one lowercase letter(a-z)
        case 6:
            return ("Password should contain at"
                    + " least one lowercase letter(a-z)");
        }

        return ("");
    }
}

// Driver Class
public class PasswordValidator {

    // A utility function to check
    // whether a password is valid or not
    public static void isValid(String password)
        throws InvalidPasswordException
    {

        // for checking if password length
        // is between 8 and 15
        if (!((password.length() >= 8)
              && (password.length() <= 15))) {
            throw new InvalidPasswordException(1);
        }

        // to check space
        if (password.contains(" ")) {
            throw new InvalidPasswordException(2);
        }
        if (true) {
            int count = 0;

            // check digits from 0 to 9
            for (int i = 0; i <= 9; i++) {

                // to convert int to string
                String str1 = Integer.toString(i);

                if (password.contains(str1)) {
                    count = 1;
                }
            }
            if (count == 0) {
                throw new InvalidPasswordException(3);
            }
        }

        // for special characters
        if (!(password.contains("@") || password.contains("#")
              || password.contains("!") || password.contains("~")
              || password.contains("$") || password.contains("%")
              || password.contains("^") || password.contains("&")
              || password.contains("*") || password.contains("(")
              || password.contains(")") || password.contains("-")
              || password.contains("+") || password.contains("/")
              || password.contains(":") || password.contains(".")
              || password.contains(", ") || password.contains("<")
              || password.contains(">") || password.contains("?")
              || password.contains("|"))) {
            throw new InvalidPasswordException(4);
        }

        if (true) {
            int count = 0;

            // checking capital letters
            for (int i = 65; i <= 90; i++) {

                // type casting
                char c = (char)i;

                String str1 = Character.toString(c);
                if (password.contains(str1)) {
                    count = 1;
                }
            }
            if (count == 0) {
                throw new InvalidPasswordException(5);
            }
        }

        if (true) {
            int count = 0;

            // checking small letters
            for (int i = 90; i <= 122; i++) {

                // type casting
                char c = (char)i;
                String str1 = Character.toString(c);

                if (password.contains(str1)) {
                    count = 1;
                }
            }
            if (count == 0) {
                throw new InvalidPasswordException(6);
            }
        }

        // The password is valid
    }

    // Driver code
    public static void main(String[] args)
    {

        String password1 = "GeeksForGeeks";

        try {
            System.out.println("Is Password "
                               + password1 + " valid?");
            isValid(password1);
            System.out.println("Valid Password");
        }
        catch (InvalidPasswordException e) {
            System.out.print(e.getMessage());
            System.out.println(e.printMessage());
        }

        String password2 = "Geek007@GFG";
        try {
            System.out.println("\nIs Password "
                               + password2 + " valid?");
            isValid(password2);
            System.out.println("Valid Password");
        }
        catch (InvalidPasswordException e) {
            System.out.print(e.getMessage());
            System.out.println(e.printMessage());
        }
    }
}

Output:

Is Password GeeksForGeeks valid?
Invalid Password: Password should contain at least one digit(0-9)

Is Password Geek007@GFG valid?
Valid Password