Problem
You would like to select the contents of all comments in an HTML (or XML) document using Java Regular Expressions.
For instance:
<html>
<!– FOR ME TO SELECT –>
</html>
Solution
There is a powerful regular expression, which can be found on this page.
static final String commentRegex = “(// )?\\<![ \\r\\n\\t]*(–([^\\-]|[\\r\\n]|-[^\\-])*–[ \\r\\n\\t]*)\\>”;
However, this regular expression might lead to your application to ‘hang’ if there are (bad, bad input) documents with starting comments without matching comment end, like:
<html>
<!– I AM SO EVIL
</html>
To prevent your application to hang in this case, you can search for the beginnings and ends of comments with two separate matchers:
static final String matchCommentStart = “\\<![ \\r\\n\\t]*–“;
static final String matchCommentEnd = “–[ \\r\\n\\t]*\\>”;
You can find a live example for this code in this class.
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