How to escape a square bracket for Pattern compilation

Question

Hello guys. am new to regular expression.

I have comma seperated list of regular expressions like: .{8},[0-9],[^0-9A-Za-z ],[A-Z],[a-z]. I have done a split on the comma. Now am trying to match of this regex against a generated password. The problem is that Pattern.compile does not like square brackets that is not escaped. Can some please give me a simple function that takes a string as so: [0-9] and returns the escaped string \[0-9\]. Thanks again

Answer 1

You can use Pattern.quote(String).

Answer 2

You can use the \Q and \E special characters...anything between \Q and \E is automatically escaped.

\Q[0-9]\E

Answer 3

Pattern.compile() likes square brackets just fine. If you take the string

".{8},[0-9],[^0-9A-Za-z ],[A-Z],[a-z]"

and split it on commas, you end up with five perfectly valid regexes: the first one matches eight non-line-separator characters, the second matches an ASCII digit, and so on. Unless you really want to match strings like ".{8}" and "[0-9]", I don't see why you would need to escape anything.