Read input from user and ignore the spaces between words, converting letters to telephone numbers

I've been trying to figure out how to ignore the blank space/digits/letters by using the character.isDigit & character.isLetter method when the users enters a String.. Can you guys please advise me?

When I tried the input with GETLOAN (Without the space) it works well... But when I enter a space between e..g. Get Loan, the program shows an error..

public static void main(String[] args) {

    String letters;
    char phoneDigit;

    Scanner kb = new Scanner(System.in);

    System.out.println("Enter letters : ");
    letters = kb.next();

    for (int i = 0; i < 7; i++) {

        phoneDigit = letters.charAt(i);

        // Using character.isDigit...
        if (Character.isDigit(phoneDigit) == true || Character.isLetter(phoneDigit) == true);
        {

            if (i == 3) {
                System.out.println("-");
            } //If 

            if (phoneDigit >= 'A' && phoneDigit <= 'C'
                    || phoneDigit >= 'a' && phoneDigit <= 'c') {

                System.out.println("2");

            } else if (phoneDigit >= 'D' && phoneDigit <= 'F'
                    || phoneDigit >= 'd' && phoneDigit <= 'f') {

                System.out.println("3");

            } else if (phoneDigit >= 'G' && phoneDigit <= 'I'
                    || phoneDigit >= 'g' && phoneDigit <= 'i') {

                System.out.println("4");

            } else if (phoneDigit >= 'J' && phoneDigit <= 'L'
                    || phoneDigit >= 'j' && phoneDigit <= 'l') {

                System.out.println("5");

            } else if (phoneDigit >= 'M' && phoneDigit <= 'O'
                    || phoneDigit >= 'm' && phoneDigit <= 'o') {

                System.out.println("6");

            } else if (phoneDigit >= 'P' && phoneDigit <= 'S'
                    || phoneDigit >= 'p' && phoneDigit <= 's') {

                System.out.println("7");

            } else if (phoneDigit >= 'T' && phoneDigit <= 'V'
                    || phoneDigit >= 't' && phoneDigit <= 'v') {

                System.out.println("8");

            } else if (phoneDigit >= 'W' && phoneDigit <= 'Z'
                    || phoneDigit >= 'W' && phoneDigit <= 'z') {

                System.out.println("9");
            } // If
        } // If
    } // For loop

} //PSVM