Regex – replace start and end character sequences Code Answer

hope this is a reasonable way to try explain my goal.

My goal is to update strings from

"unchanged DETECT_OPEN blah DETECT_CLOSE unchanged"

to

"unchanged UPDATED_OPEN blah UPDATED_CLOSE unchanged"

So for

DETECT_OPEN = [
DETECT_CLOSE = ]

UPDATED_OPEN = <
UPDATED_CLOSE = >

on an input string of

"this stays the same [i am wrapped] nothing to do here"

after processing it is

"this stays the same <i am wrapped> nothing to do here"

Is there a good way to tackle this with regex? I’m in java; so a java specific example would be ideal; but any regex is welcome; I’ll be happy to try take it from there.

Not sure if it’ll make any difference; but the OPEN and CLOSE markers can be more than 1 character; and not equal in length.

So for example

DETECT_OPEN = ||
DETECT_CLOSE = |

Simple example:

 "this stays the same ||i am wrapped| nothing to do here"

And the reason I can’t use multiple find replaces – is for scenarios like

"this isn't an open || because it doesn't close. This open || is  closed |, this close | was never opened"

So after processing it would be

"this isn't an open || because it doesn't close. This open < is  closed >, this close | was never opened"

Thanks, Brent

Answer

You can do this using a capture group:

String replaced = input.replaceAll("\[(.*?)\]", "<$1>");

This creates a new string, with the [...] replaced with <...>. The $1 refers to the expression that was captured within the first matched (...) in the pattern.