Luhn Algorithm With Java

Luhn Algorithm is a method to check the validation of Credit Card.
Almost all credit card in the world using this method for generating card number.

This is my implementation using Java:

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public class LuhnValidator { public static boolean isValidCardNumber(String cardNumber) { if(cardNumber==null) return false; cardNumber = cardNumber.trim(); if(cardNumber.equals("")) return false; int res = 0; boolean odd=true; for(int i=cardNumber.length()-1;>=0;i--) { char c = cardNumber.charAt(i); if(c>='0' && c<='9') { int v = c - '0'; if(!odd) { v *= 2; v = (v/10) + (v%10); } odd = !odd; res += v; } // skip space else if(c!=' ') { // other character is not valid return false; } } return (res%10) == 0; } public static void main(String []args) { System.out.println(LuhnValidator.isValidCardNumber(null)); System.out.println(LuhnValidator.isValidCardNumber(" ")); System.out.println(LuhnValidator.isValidCardNumber("4111 1111 1111 1111")); System.out.println(LuhnValidator.isValidCardNumber("4124123143215674")); System.out.println(LuhnValidator.isValidCardNumber("4184126643215675")); } }