Regex for determining credit cards in Android

Question

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!

you've linked to a question that totally answers the various aspects of your question. — njzk2, Jan 29 '15 at 18:24
My question is why doesn't that code work for me. I'm thinking that the issue is with Java or android studio — AIntel, Jan 29 '15 at 19:43
post your log. What input are you trying to match against that regex ? — njzk2, Jan 29 '15 at 20:10
Correct it does right now, I've tested for other cards as well individually. I'm now using EagleEye's code, which simply checks if the credit card number matches any of the patterns however the log still says "discover" — AIntel, Jan 29 '15 at 20:21
your visa pattern requires at least 8 numbers in the input to recognize a visa. Which is why your input is not recognized as a visa (yet) — njzk2, Jan 29 '15 at 20:33

score 22 · Accepted Answer · edited May 23 '17 at 12:33

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.

Sorry my bad. Have updated the answer. You need to remove the added spaces from the card number. — Vilas, Jan 29 '15 at 18:20
While you're right there shouldn't be spaces, i am typing the credit card in without spaces and it still doesn't work. Is there a chance that certain regexp don't work on Java 7? — AIntel, Jan 29 '15 at 19:45
If I want to check which creditcard number belongs, Visa or master? — Nathiel Barros, Aug 16 '17 at 22:22

score -1 · Answer 2 · answered Jan 29 '15 at 06:00

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();
}

}

The 'applyAlgo' variable is basically redundant, as you throw an exception when most of the paths that set it to 'true' aren't taken, and it wouldn't hurt to apply it in the other cases. I'm also violently against abbreviating this word. The word is 'algorithm', from a proper name. — user207421, Jan 29 '15 at 06:20
This isn't what I am trying to do, I'm trying to figure out what type of credit card is being entered, as the user is typing. I'm already implementing a validation algorithm to determine if the credit card is valid. — AIntel, Jan 29 '15 at 18:18

Regex for determining credit cards in Android

2 Answers2

Linked