I want to create a character class that doesn't match any character. For now, I have been representing the pattern like this:
Pattern p = Pattern.compile("[a&&b]");
or even
Pattern p = Patterncompile("[^\\x{0}-\\x{10FFFF}]");
Is there a proper way to do this?
Note: there is no need to provide an alternative solution (negative lookahead, etc) that doesn't involve a character class. I'm just interested in knowing if there is a "right" way to do it.
Update: I'm implementing a feature which prints to the user the simplified version of what he inputted in the first place. Since I am simplifying character classes, my current version would just print [] for an input such as [a&&b]. If we parse [] again, it will throw an error, which is not what I want. Hence, that's why I wanted to know if there is a proper way to do it that does not alter the user input by showing him things like ^$
Altough that does not make much sense, you may use character class subtraction feature inside a character class to actually define a char and subtract it - then this class will not be able to match anything.
Example:
[a&&[^a]]
Since the character class should only match a, and the a is substracted, this pattern will not match anything.