Hi Friend,

Try the following code:

import java.util.*;
public  class CheckCreditCardNumber {

  public static boolean isValid (String cardNumber) {
    int sum = 0;
    int digit = 0;
    int addend = 0;
    boolean timesTwo = false;
    StringBuffer buffer = new StringBuffer ();
    char c;
    for (int i = 0; i < cardNumber.length (); i++) {
      c = cardNumber.charAt (i);
      if (Character.isDigit (c)) {
        buffer.append (c);
      }
      if (Character.isLetter (c)) {
          System.out.println("Enter only numbers!");
        System.exit(0);
      }
      }
    String st=buffer.toString ();
    for (int i = st.length () - 1; i >= 0; i--) {
      digit = Integer.parseInt (st.substring (i, i + 1));
      if (timesTwo){
        addend = digit * 2;
        if (addend > 9) {
          addend -= 9;
        }
      }
      else {
        addend = digit;
      }
      sum += addend;
      timesTwo = !timesTwo;
    }
    int modulus = sum % 10;
    return modulus == 0;
  }
  public static void main (String[] args) {
    Scanner input=new Scanner(System.in);
    System.out.print("Enter Credit Card Number: ");
    String cardNumber = input.nextLine();
    boolean valid = CheckCreditCardNumber.isValid(cardNumber);
    if(valid){
    System.out.println ("Credit Card Number is Valid");
    }
    else{
    System.out.println ("Invalid Credit Card Number!");
    }
  }
}

Thanks