Binary String Regex Control Position

Question

I want to write a regex such that it matches all binary strings of length zero or more. The requirement is that the odd position must be 1 and even position can be either 1 or 0.

I am not sure how to control positions with regex?

My idea is something like ([1]+[01]*)+

Sample:

10101
11111

Can you please add some sample binary strings for better understanding? — Ankur Shanbhag
– Ankur Shanbhag, Commented Aug 4, 2013 at 7:25

Rohit Jain · Accepted Answer · 2013-08-04 07:32:22Z

2

You should remove that quantifier from inside. Also, since you want to match 0 length string, you need to use * quantifier on complete regex, instead of +.

Try using the following regex:

(1[01]?)*

This will match:

1 at first place
Then 0 or 1 in the 2nd place.
0 or more repetition, will make every odd position filled with 1, and even position can contain 0 or 1.
[01] is optional to match odd length string.

edited Aug 4, 2013 at 7:32

answered Aug 4, 2013 at 7:27

Rohit Jain

214k45 gold badges419 silver badges534 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Mat.S Over a year ago

Just to confirm if it is round bracket (), then * or + means repetition but if it is square bracket [], then * or + means combination?

Rohit Jain Over a year ago

@Mat.S. This is to do with the character class. A character class can matches a single character out of all the character inside []. So, + or *, is repetition only. Just that, it will match repetition of any character from [].

Ankur Shanbhag · Accepted Answer · 2013-08-04 07:30:35Z

1

try using this :

String data = "10111";
        Pattern pattern = Pattern.compile("(1[01]?)*");

        Matcher matcher = pattern.matcher(data);
        while (matcher.find()) {
            // Indicates match is found. Do further processing
            System.out.println(matcher.group());
        }

answered Aug 4, 2013 at 7:30

Ankur Shanbhag

7,8042 gold badges31 silver badges38 bronze badges

Collectives™ on Stack Overflow

Binary String Regex Control Position

2 Answers 2

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest