Type CTRL+F in the search box in idea
\/\*\*(\s|.)*?\*\/
\s : matches invisible characters
. : matches any single character except '\n'
? : When the character immediately follows any one of the other qualifiers (*,+,?, {n}, {n,}, {n,m}), the matching pattern is non-greedy. Match fewer characters.
Search bar uses regular expressions to search
(/\*([^*]|[\r\n]|(\*+([^*/]|[\r\n])))*\*+/|[ \t]*//.*)
The code that will search for all comments can be replaced with spaces.
or search
(/\*([^*]|[\r\n]|(\*+([^*/]|[\r\n])))*\*+/)
Just search for the first and last comments
Also searching for whitespace lines is
\n\n
Then global replace can remove the code space line.