Die Luhn Check Data Algorithm in Java

Die Luhn Prüfziffer-Algorithmus in Java

  //------------------------------------------------ --------- 
  / / Die Kontrollen für gültige Kreditkarte Zahl mit Luhn-Algorithmus 
  //------------------------------------------------ --------- 

  öffentlichen abstrakte Klasse LuhnCheck ( 

    //-------------------------------- 
    / / Filter aus nicht-stelligen Zeichen 
    //-------------------------------- 

    private static String getDigitsOnly (String s) ( 
      StringBuffer digitsOnly = new StringBuffer (); 
      char c; 
      for (int i = 0; i <s.length (); i + +) ( 
        c = s.charAt (i); 
        if (Character.isDigit (c)) ( 
          digitsOnly.append (c); 
        ) 
      ) 
      Rückkehr digitsOnly.toString (); 
    ) 

    //------------------- 
    / / Perform Luhn Check 
    //------------------- 

    public static boolean isValid (String cardNumber) ( 
      String digitsOnly = getDigitsOnly (cardNumber); 
      int sum = 0; 
      int digit = 0; 
      Summand int = 0; 
      boolean timesTwo = false; 

      for (int i = digitsOnly.length () - 1, i> = 0; i -) ( 
        Stelle = Integer.parseInt (digitsOnly.substring (i, i + 1)); 
        if (timesTwo) ( 
          Summand = digit * 2; 
          if (Summand> 9) ( 
            Summand -= 9; 
          ) 
        ) 
        else ( 
          Summand = digit; 
        ) 
        Summe + = Summand; 
        timesTwo =! timesTwo; 
      ) 

      int-Modul = Summe% 10; 
      Rückkehr-Modul == 0; 

    ) 

    //----- 
    / / Test 
    //----- 

    public static void main (String [] args) ( 
      String cardNumber = "4408 0412 3456 7890"; 
      boolean gültig = LuhnCheck.isValid (cardNumber); 
      System.out.println (cardNumber + ":" + gültig); 
      cardNumber = "4408 0412 3456 7893"; 
      gültig = LuhnCheck.isValid (cardNumber); 
      System.out.println (cardNumber + ":" + gültig); 
      cardNumber = "4417 1234 5678 9112"; 
      gültig = LuhnCheck.isValid (cardNumber); 
      System.out.println (cardNumber + ":" + gültig); 
      cardNumber = "4417 1234 5678 9113"; 
      gültig = LuhnCheck.isValid (cardNumber); 
      System.out.println (cardNumber + ":" + gültig); 
    ) 

  )