Java Regex to replace only part of string (url)

Question

I want to replace only numeric section of a string. Most of the cases it's either full URL or part of URL, but it can be just a normal string as well.

/users/12345 becomes /users/XXXXX
/users/234567/summary becomes /users/XXXXXX/summary
/api/v1/summary/5678 becomes /api/v1/summary/XXXX
http://example.com/api/v1/summary/5678/single becomes http://example.com/api/v1/summary/XXXX/single

Notice that I am not replacing 1 from /api/v1

So far, I have only following which seem to work in most of the cases:

input.replaceAll("/[\\d]+$", "/XXXXX").replaceAll("/[\\d]+/", "/XXXXX/");

But this has 2 problems:

The replacement size doesn't match with the original string length.
The replacement character is hardcoded.

Is there a better way to do this?

anubhava · Accepted Answer · 2020-03-16 19:08:43Z

3

In Java you can use:

str = str.replaceAll("(/|(?!^)\\G)\\d(?=\\d*(?:/|$))", "$1X");

RegEx Demo

RegEx Details:

\G asserts position at the end of the previous match or the start of the string for the first match.
(/|(?!^)\\G): Match / or end of the previous match (but not at start) in capture group #1
\\d: Match a digit
(?=\\d*(?:/|$)): Ensure that digits are followed by a / or end.
Replacement: $1X: replace it with capture group #1 followed by X

edited Mar 16, 2020 at 19:08

answered Mar 16, 2020 at 18:59

anubhava

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3 Comments

oriberu Over a year ago

Very nice, but you'll need to close on either a slash or the end of string in order to avoid matching numbers followed by non-numeric characters.

anubhava Over a year ago

Sure, (/|(?!^)\G)\d(?=\d*(?:/|$)) can be used to ensure that but this case wasn't specifically mentioned in OP's requirements.

oriberu Over a year ago

Maybe I misinterpreted the OP's first sentence: "I want to replace only numeric section of a string."

Jan · Accepted Answer · 2020-03-16 18:57:00Z

0

Not a Java guy here but the idea should be transferrable. Just capture a /, digits and / optionally, count the length of the second group and but it back again.

So

(/)(\d+)(/?)

becomes

$1XYZ$3

See a demo on regex101.com and this answer for a lambda equivalent to e.g. Python or PHP.

edited Mar 16, 2020 at 18:57

answered Mar 16, 2020 at 18:51

Jan

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1 Comment

Garbage Over a year ago

Thanks Jan for the reply. But Java regex are little different than other languages are not really mapped 1-1. There is another answer by @anubhava which works.

Catalina Chircu · Accepted Answer · 2020-03-16 19:13:59Z

0

First of all you need something like this :

String new_s1 = s3.replaceAll("(\\/)(\\d)+(\\/)?", "$1XXXXX$3");

answered Mar 16, 2020 at 19:13

Catalina Chircu

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2 Comments

Garbage Over a year ago

Thanks for the reply. However this does not solve any of the 2 problems mentioned in the question. Please refer to @anubhava's answer which works perfectly for these.

Catalina Chircu Over a year ago

Indeed, he provided the best answer. Hat off!

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