This might be a piece of cake for java experts. Please help me out:
I have a block of comments in my program like this:
/*********
block of comments - line 1
line 2
.....
***/
How could I retrieve "block of comments" using regex?
thanks.
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3 Answers
Something like this should do:
String str =
"some text\n"+
"/*********\n" +
"block of comments - line 1\n" +
"line 2\n"+
"....\n" +
"***/\n" +
"some more text";
Pattern p = Pattern.compile("/\\*+(.*?)\\*+/", Pattern.DOTALL);
Matcher m = p.matcher(str);
if (m.find())
System.out.println(m.group(1));
(DOTALL says that the . in the pattern should also match new-line characters)
Prints:
block of comments - line 1
line 2
....
1 Comment
David Stocking
messes up if you put /* in a string in the code. NOONE should do that but im just saying.
Pattern regex = Pattern.compile("/\\*[^\\r\\n]*[\\r\\n]+(.*?)[\\r\\n]+[^\\r\\n]*\\*+/", Pattern.DOTALL);
This works because comments can't be nested in Java.
It is important to use a reluctant quantifier (.*?) or we will match everything from the first comment to the last comment in a file, regardless of whether there is actual code in-between.
/\* matches /*
[^\r\n]* matches whatever else is on the rest of this line.
[\r\n]+ matches one or more linefeeds.
.*? matches as few characters as possible.
[\r\n]+ matches one or more linefeeds.
[^\r\n]* matches any characters on the line of the closing */.
\*/ matches */.
Comments
Not sure about the multi-line issues, but it were all on one line, you could do this:
^\/\*.*\*\/$
That breaks down to:
^ start of a line
\/\*+ start of a comment, one or more *'s (both characters escaped)
.* any number of characters
\*+\/ end of a comment, one or more *'s (both characters escaped)
$ end of a line
By the way, it's "regex" not "regrex" :)
2 Comments
Ethan Shepherd
I think both your \* need to be \*+
ChessWhiz
@Ethan Thanks. Didn't realize that those extra *'s shouldn't be matched.