Regex Sublime to Java regex

Question

i have this regex to delete comments in .c file(sublime 3 regex)

(^\/\/.*)|(\s+\/\/.*)|((\/\*)(.|\n)+?(\*\/)) 

Can i use this regex in java to use it programmatically? If not, what regex should i use? (PS i know, question us stupid a bit, but i don't know how to regex at all)

Answer 1

Note that you have too many redundant capture groups inside the pattern, and the (.|\\n)+? construct is very inefficient and may cause serious issues in Java (as with any other regex engine).

You can use a more streamlines expression that should not cause much redundant backtracking:

(?:^|\s+)//.*|/\*[^*]*\*+(?:[^/*][^*]*\*+)*/

See the regex demo . Use it with Pattern.MULTILINE flag (or add (?m) at the start of the pattern).

Pattern explanation :

• (?:^|\\s+)//.* - (your 2 (^\\/\\/.*)|(\\s+\\/\\/.*) branches merged) single line comments at the start of a string or after the first 1+ whitespaces followed with // substring (including these whitespaces and forward slashes)
• | - or
• /\\*[^*]*\\*+(?:[^/*][^*]*\\*+)*/ - match multiline /**/ comments

Java declaration:

String pattern = "(?m)(?:^|\\s+)//.*|/\\*[^*]*\\*+(?:[^/*][^*]*\\*+)*/";

And a sample code :

String s =  "// Comment\ntex test\nMore text here // and comment 2\n/* More comments\nhere and\nhere */";
String pattern = "(?m)(?:^|\\s+)//.*|/\\*[^*]*\\*+(?:[^/*][^*]*\\*+)*/";
System.out.println(s.replaceAll(pattern, "")); 

Answer 2

This should work : (?:/\\\\*(?:[^*]|(?:\\\\*+[^*/]))*\\\\*+/)|(?://.*)

Ideone Demo