How to substitute blanks between certain patterns using regex

Issue

I want to substitute the blanks between the $# and the ending #.

Test String:

This is my variable A $#testpattern 1# and this is variable B $#testpattern 2 with multiple blanks#

Expected result:

This is my variable A $#testpattern1# and this is variable B $#testpattern2withmultipleblanks#

I got it to work when it only has one blank but with more than one it does not work.

Current Regex:

/(?<=\$#)(\w*?)(\s*?)(\w*?)(?=#)

Solution

Java supports a finite quantifier in a lookbehind assertion, so you can add optional word characters or spaces to it [\w\s]{0,100} and for the lookahead you can add only [\w\s]* matching 1 or more whitespace characters in between.

(?<=\$#[\w\s]{0,100})\s+(?=[\w\s]*#)

For example

String string = "This is my variable A $#testpattern 1# and this is variable B $#testpattern 2 with multiple blanks#";
System.out.println(string.replaceAll("(?<=\\$#[\\w\\s]{0,100})\\s+(?=[\\w\\s]*#)", ""));

Output

This is my variable A $#testpattern1# and this is variable B $#testpattern2withmultipleblanks#

See a Java demo and a Regex demo.

Answered By - The fourth bird