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I have a string for e.g.
String src = "How are things today /* this is comment *\*/ and is your code /*\* this is another comment */ working?" I want to remove /* this is comment *\*/ and /** this is another comment */ substrings from the src string.
I tried to use regex but failed due to less experience.
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Multiline option, it matches either the newline character ( \n ) or the end of the input string. It does not, however, match the carriage return/line feed character combination.
The m flag indicates that a multiline input string should be treated as multiple lines. For example, if m is used, ^ and $ change from matching at only the start or end of the entire string to the start or end of any line within the string. You cannot change this property directly.
To match a character having special meaning in regex, you need to use a escape sequence prefix with a backslash ( \ ). E.g., \. matches "." ; regex \+ matches "+" ; and regex \( matches "(" . You also need to use regex \\ to match "\" (back-slash).
A multiline comment starts with /* and then ends with */. A regular comment can be made by either // or a # in front of text, but it can only support one line. If you use a multiline comment, use can make a comment that's as many lines as you want. Posting to the forum is only allowed for members with active accounts.
The best multiline comment regex is an unrolled version of (?s)/\*.*?\*/ that looks like
String pat = "/\\*[^*]*\\*+(?:[^/*][^*]*\\*+)*/"; See the regex demo and explanation at regex101.com.
In short,
/\* - match the comment start /* [^*]*\*+ - match 0+ characters other than * followed with 1+ literal * (?:[^/*][^*]*\*+)* - 0+ sequences of: [^/*][^*]*\*+ - not a / or * (matched with [^/*]) followed with 0+ non-asterisk characters ([^*]*) followed with 1+ asterisks (\*+)/ - closing / David's regex needs 26 steps to find the match in my example string, and my regex needs just 12 steps. With huge inputs, David's regex is likely to fail with a stack overflow issue or something similar because the .*? lazy dot matching is inefficient due to lazy pattern expansion at each location the regex engine performs, while my pattern matches linear chunks of text in one go.
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Try using this regex (Single line comments only):
String src ="How are things today /* this is comment */ and is your code /* this is another comment */ working?"; String result=src.replaceAll("/\\*.*?\\*/","");//single line comments System.out.println(result); REGEX explained:
Match the character "/" literally
Match the character "*" literally
"." Match any single character
"*?" Between zero and unlimited times, as few times as possible, expanding as needed (lazy)
Match the character "*" literally
Match the character "/" literally
Alternatively here is regex for single and multi-line comments by adding (?s):
//note the added \n which wont work with previous regex String src ="How are things today /* this\n is comment */ and is your code /* this is another comment */ working?"; String result=src.replaceAll("(?s)/\\*.*?\\*/",""); System.out.println(result); Reference:
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