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java – Regex for determining credit cards in Android

Posted by: admin June 15, 2020 Leave a comment

Questions:

I’m really new to regex but I think my problem might go beyond that at the moment. As the title says, I’m trying to determine if a credit card is visa, amex, master card etc.

I looked at this post which gave the regular expression for each of the card types:

How do you detect Credit card type based on number?

This is the code I then used but it doesn’t do anything at all:

etCCNum.addTextChangedListener(new TextWatcher() {
            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {



            }

            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {
                Log.d("DEBUG", "beforeTextChanged : "+s);

            }

            @Override
            public void afterTextChanged(Editable s) {
                Pattern pattern = Pattern.compile("^6(?:011|5[0-9]{2})[0-9]{3,}$");
                Log.d("DEBUG", "afterTextChanged : "+s);
                String ccNum = s.toString();
                Matcher matcher = pattern.matcher(ccNum);
               if(matcher.matches()){
                   Log.d("DEBUG", "afterTextChanged : discover");
               }

            }
        });

The regexp in the pattern.compile function is for determining Discover cards according to the post above. I’ve noticed that I really can’t get anything to work other than the “^” in regex (i.e (“^4” – visa, “^6001” discover) however this is obviously not sufficient in the case of editing for example. Any ideas what’s up? I thought this could be an issue with my Java, but I am running Java 7

I might want to make this a new question, but I am also wondering how regex can be used to get spacing correct for various credit cards even if a user goes back and edits the number (xxxx xxxx xxxx xxxx)

EDIT: Added the DEBUG log from above. My input is a few digits that should associate with certain credit cards. Currently I am using Eagle Eye’s code provided below (which should also work for detecting that the input is ONE of the card types):

final ArrayList listOfPattern=new ArrayList();

String ptVisa = "^4[0-9]{6,}$";
listOfPattern.add(ptVisa);
String ptMasterCard = "^5[1-5][0-9]{5,}$";
listOfPattern.add(ptMasterCard);
String ptAmeExp = "^3[47][0-9]{5,}$";
listOfPattern.add(ptAmeExp);
String ptDinClb = "^3(?:0[0-5]|[68][0-9])[0-9]{4,}$";
listOfPattern.add(ptDinClb);
String ptDiscover = "^6(?:011|5[0-9]{2})[0-9]{3,}$";
listOfPattern.add(ptDiscover);
String ptJcb = "^(?:2131|1800|35[0-9]{3})[0-9]{3,}$";
listOfPattern.add(ptJcb);


etCCNum.addTextChangedListener(new TextWatcher() {
    @Override
    public void onTextChanged(CharSequence s, int start, int before, int count) {



    }

    @Override
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {
        Log.d("DEBUG", "beforeTextChanged : "+s);

    }

    @Override
    public void afterTextChanged(Editable s) {
        Log.d("DEBUG", "afterTextChanged : "+s);
        String ccNum = s.toString();
        for(String p:listOfPattern){
            if(ccNum.matches(p)){
                Log.d("DEBUG", "afterTextChanged : discover");
                break;
            }
        }

    }
});

Log:

01-29 15:16:41.932  26194-26194/com.x.x D/DEBUG﹕ beforeTextChanged :
01-29 15:16:41.933  26194-26194/com.x.x D/DEBUG﹕ afterTextChanged : 4
01-29 15:16:46.815  26194-26194/com.x.x D/DEBUG﹕ beforeTextChanged : 4
01-29 15:16:46.816  26194-26194/com.x.x D/DEBUG﹕ afterTextChanged :
01-29 15:16:50.925  26194-26194/com.x.x D/DEBUG﹕ beforeTextChanged :
01-29 15:16:50.926  26194-26194/com.x.x D/DEBUG﹕ afterTextChanged : 6
01-29 15:16:51.542  26194-26194/com.x.x D/DEBUG﹕ beforeTextChanged : 6
01-29 15:16:51.543  26194-26194/com.x.x D/DEBUG﹕ afterTextChanged : 60
01-29 15:16:51.883  26194-26194/com.x.x D/DEBUG﹕ beforeTextChanged : 60
01-29 15:16:51.883  26194-26194/com.x.x D/DEBUG﹕ afterTextChanged : 600
01-29 15:16:52.928  26194-26194/com.x.x D/DEBUG﹕ beforeTextChanged : 600
01-29 15:16:52.929  26194-26194/com.x.x D/DEBUG﹕ afterTextChanged : 6001
01-29 15:16:55.781  26194-26194/com.x.x D/DEBUG﹕ beforeTextChanged : 6001
01-29 15:16:55.782  26194-26194/com.x.x D/DEBUG﹕ afterTextChanged : 600
01-29 15:16:56.206  26194-26194/com.x.x D/DEBUG﹕ beforeTextChanged : 600
01-29 15:16:56.206  26194-26194/com.x.x D/DEBUG﹕ afterTextChanged : 60
01-29 15:16:57.659  26194-26194/com.x.x D/DEBUG﹕ beforeTextChanged : 60
01-29 15:16:57.660  26194-26194/com.x.x D/DEBUG﹕ afterTextChanged : 605
01-29 15:16:59.297  26194-26194/com.x.x D/DEBUG﹕ beforeTextChanged : 605
01-29 15:16:59.298  26194-26194/com.x.x D/DEBUG﹕ afterTextChanged : 60
01-29 15:16:59.527  26194-26194/com.x.x D/DEBUG﹕ beforeTextChanged : 60
01-29 15:16:59.527  26194-26194/com.x.x D/DEBUG﹕ afterTextChanged : 6
01-29 15:17:00.314  26194-26194/com.x.x D/DEBUG﹕ beforeTextChanged : 6
01-29 15:17:00.314  26194-26194/com.x.x D/DEBUG﹕ afterTextChanged : 65

You’d expect the log “discover” to come out a few times for the different digits I’ve entered. The above log shows me typing in the first few digits of a visa card and a discover card.

EDIT ANSWER FOUND: I simply wasn’t typing in enough digits for the card to be recognized!

How to&Answers:

According to one of the answers in the thread, The cards can be validated based on following data.

Visa: ^4[0-9]{6,}$ Visa card numbers start with a 4.

MasterCard: ^5[1-5][0-9]{5,}$ MasterCard numbers start with the numbers 51 through 55, but this will only detect MasterCard credit cards; there are other cards issued using the MasterCard system that do not fall into this IIN range.

American Express: ^3[47][0-9]{5,}$ American Express card numbers start with 34 or 37.

Diners Club: ^3(?:0[0-5]|[68][0-9])[0-9]{4,}$ Diners Club card numbers begin with 300 through 305, 36 or 38. There are Diners Club cards that begin with 5 and have 16 digits. These are a joint venture between Diners Club and MasterCard, and should be processed like a MasterCard.

Discover: ^6(?:011|5[0-9]{2})[0-9]{3,}$ Discover card numbers begin with 6011 or 65.

JCB: ^(?:2131|1800|35[0-9]{3})[0-9]{3,}$ JCB cards begin with 2131, 1800 or 35.

So you need to create separate pattern for each case. You can do as follows.

ArrayList<String> listOfPattern=new ArrayList<String>();

String ptVisa = "^4[0-9]{6,}$";
listOfPattern.add(ptVisa);
String ptMasterCard = "^5[1-5][0-9]{5,}$";
listOfPattern.add(ptMasterCard);
String ptAmeExp = "^3[47][0-9]{5,}$";
listOfPattern.add(ptAmeExp);
String ptDinClb = "^3(?:0[0-5]|[68][0-9])[0-9]{4,}$";
listOfPattern.add(ptDinClb);
String ptDiscover = "^6(?:011|5[0-9]{2})[0-9]{3,}$";
listOfPattern.add(ptDiscover);
String ptJcb = "^(?:2131|1800|35[0-9]{3})[0-9]{3,}$";
listOfPattern.add(ptJcb);
}

and then,

@Override
public void afterTextChanged(Editable s) {
Log.d("DEBUG", "afterTextChanged : "+s);
String ccNum = s.toString();
   for(String p:listOfPattern){
      if(ccNum.matches(p)){
         Log.d("DEBUG", "afterTextChanged : discover");
         break;
      }
   }
}

And for your last question, The following thread should help you.

Format credit card in edit text in android

EDIT:

If the card number is 16 digits for example, After applying the logic to add spaces after 4 digits, you need to remove those spaces when you process the actual card number. Then only the above logic will work.

Hope this helps.

Answer:

Use following class to validate you card.

public class Validator {


public static final byte VISA = 0;
public static final byte MASTERCARD = 1;
public static final byte AMEX = 2;
public static final byte DINERS_CLUB = 3;
public static final byte CARTE_BLANCHE = 4;
public static final byte DISCOVER = 5;
public static final byte ENROUTE = 6;
public static final byte JCB = 7;

public static boolean validate(final String credCardNumber, final byte type) {
    String creditCard = credCardNumber.trim();
    boolean applyAlgo = false;
    switch (type) {
        case VISA:
            // VISA credit cards has length 13 - 15
            // VISA credit cards starts with prefix 4
            if (creditCard.length() >= 13 && creditCard.length() <= 16
                    && creditCard.startsWith("4")) {
                applyAlgo = true;
            }
            break;
        case MASTERCARD:
            // MASTERCARD has length 16
            // MASTER card starts with 51, 52, 53, 54 or 55
            if (creditCard.length() == 16) {
                int prefix = Integer.parseInt(creditCard.substring(0, 2));
                if (prefix >= 51 && prefix <= 55) {
                    applyAlgo = true;
                }
            }
            break;
        case AMEX:
            // AMEX has length 15
            // AMEX has prefix 34 or 37
            if (creditCard.length() == 15
                    && (creditCard.startsWith("34") || creditCard
                    .startsWith("37"))) {
                applyAlgo = true;
            }
            break;
        case DINERS_CLUB:
        case CARTE_BLANCHE:
            // DINERSCLUB or CARTEBLANCHE has length 14
            // DINERSCLUB or CARTEBLANCHE has prefix 300, 301, 302, 303, 304,
            // 305 36 or 38
            if (creditCard.length() == 14) {
                int prefix = Integer.parseInt(creditCard.substring(0, 3));
                if ((prefix >= 300 && prefix <= 305)
                        || creditCard.startsWith("36")
                        || creditCard.startsWith("38")) {
                    applyAlgo = true;
                }
            }
            break;
        case DISCOVER:
            // DISCOVER card has length of 16
            // DISCOVER card starts with 6011
            if (creditCard.length() == 16 && creditCard.startsWith("6011")) {
                applyAlgo = true;
            }
            break;
        case ENROUTE:
            // ENROUTE card has length of 16
            // ENROUTE card starts with 2014 or 2149
            if (creditCard.length() == 16
                    && (creditCard.startsWith("2014") || creditCard
                    .startsWith("2149"))) {
                applyAlgo = true;
            }
            break;
        case JCB:
            // JCB card has length of 16 or 15
            // JCB card with length 16 starts with 3
            // JCB card with length 15 starts with 2131 or 1800
            if ((creditCard.length() == 16 && creditCard.startsWith("3"))
                    || (creditCard.length() == 15 && (creditCard
                    .startsWith("2131") || creditCard
                    .startsWith("1800")))) {
                applyAlgo = true;
            }
            break;
        default:
            throw new IllegalArgumentException();
    }
    if (applyAlgo) {
        return validate(creditCard);
    }
    return false;
}

public static boolean validate(String creditCard) {
    // 4 9 9 2 7 3 9 8 7 1 6
    // 6
    // 1 x 2 = 2  = (0 + 2) = 2
    // 7
    // 8 x 2 = 16 = (1 + 6) = 7
    // 9
    // 3 x 2 = 6 = (0 + 6) = 6
    // 7
    // 2 x 2 = 4 = (0 + 4) = 4
    // 9
    // 9 X 2 = 18 = (1 + 8) = 9
    // 4
    // 6+2+7+7+9+6+7+4+9+9+4 = 70
    // return 0 == (70 % 10)
    int sum = 0;
    int length = creditCard.length();
    for (int i = 0; i < creditCard.length(); i++) {
        if (0 == (i % 2)) {
            sum += creditCard.charAt(length - i - 1) - '0';
        } else {
            sum += sumDigits((creditCard.charAt(length - i - 1) - '0') * 2);
        }
    }
    return 0 == (sum % 10);
}

private static int sumDigits(int i) {
    return (i % 10) + (i / 10);
}



public final static boolean isValidEmail(CharSequence target) {
    return !TextUtils.isEmpty(target) && android.util.Patterns.EMAIL_ADDRESS.matcher(target).matches();
}

}