Zero-padding for Integer as String after increment

Question

I need to increment by one an String that is only digits:

String current = "000433"; //After increment, will be "000434"

I have this procedure, that works properly:

private String incrementOne(String numberAsString) {
    int leftZeroCount = countLeadingZeros(numberAsString);
    Integer asInteger = Integer.parseInt(numberAsString);
    asInteger++;
    return parseStringWithNZeros(asInteger, leftZeroCount);
}

private String parseStringWithNZeros(Integer asInteger, int leftZeroCount) {
    String asString = Integer.toString(asInteger);
    for (int i = 0; i < leftZeroCount; i++)
        asString = "0" + asString;
    return asString;
}

private int countLeadingZeros(String numberAsString) {
    int count = 0;
    int i = 0;
    while (numberAsString.charAt(i) == '0' && i < numberAsString.length()) {
        count++;
        i++;
    }
    return count;
}

The process is:

Count the left zeros
Parse to Integer
Increment by one
Parse to String
Add the left zeros

The length of the number as String is unknown. I am sure that exists another easier and cleaner way, with regex or something. Which alternatives can I adopt?

Thanks.

This might be a better fit for http://codereview.stackexchange.com/ — reto, Apr 09 '15 at 07:51
Nothing wrong with that solution, except I guess you expect the next value for 000999 to be 001000 and not 0001000. Your method parse doesn't parse, it formats. So its name should be formatWithNZeros. — JB Nizet, Apr 09 '15 at 07:54
Check the post http://stackoverflow.com/questions/275711/add-leading-zeroes-to-number-in-java — HJK, Apr 09 '15 at 07:54
@user3694267 - or the original : http://stackoverflow.com/questions/473282/how-can-i-pad-an-integers-with-zeros-on-the-left — Gnoupi, Apr 09 '15 at 07:56
Thanks! @JBNizet you're right. Actually, my code is not contemplating this case. Next value for 000999 would be 0001000 in my code, but it is wrong. — Héctor, Apr 09 '15 at 08:44
I'm voting to close this question as off-topic because it belongs on codereview.stackexchange.com — Colin 't Hart, Apr 09 '15 at 09:08

score 19 · Accepted Answer · answered Apr 09 '15 at 07:54

19

How about doing it like this, using String.format():

String original = "000433";
String incremented = String.format("%0" + original.length() + "d",
            Integer.parseInt(original) + 1);

System.out.println(incremented);

answered Apr 09 '15 at 07:54

Robby Cornelissen

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Thank you. All tests passed successfully ^^ – Héctor Apr 09 '15 at 08:50
save my day .... thankssss – Atif Amin Aug 31 '18 at 08:30

score 0 · Answer 2 · answered Apr 09 '15 at 08:02

Try this:

private String incrementOne(String numberAsString) {
   int length = numberAsString.length();
   Integer asInteger = Integer.parseInt(numberAsString);
   asInteger++;
   numberAsString = asInteger.toString();
   while(numberAsString.length() < length){
      numberAsString = "0" + numberAsString;
      count ++;
   }
   return numberAsString;
}

Zero-padding for Integer as String after increment

2 Answers2