Need a regular expression for URL

Question

Regular expression: ^(udp|norm)://(?:(?:25[0-5]|2[0-4]\\d|[01]\\d\\d|\\d?\\d)(?(?=\\.?\\d)\\.)){4}:(6553[0-5]|655[0-2][0-9]\\d|65[0-4](\\d){2}|6[0-4](\\d){3}|[1-5](\\d){4}|[1-9](\\d){0,3})$
Source: udp://125.3.4.121:23456
Getting error:java.util.regex.PatternSyntaxException: Unknown inline modifier near index 54
^(udp|norm)://(?:(?:25[0-5]|2[0-4]\d|[01]\d\d|\d?\d)(?(?=\.?\d)\.)){4}:(6553[0-5]|655[0-2][0-9]\d|65[0-4](\d){2}|6[0-4](\d){3}|[1-5](\d){4}|[1-9](\d){0,3})$

Answer 1

paulcw wrote:
I can't help wondering if a simpler solution would involve creating a java.net.URL object, passing it the string to be checked, and let URL do the parsing and an initial pass at checking the syntax. Then you could query URL for individual components for further checking (e.g., getting the transfer type to make sure it's one of the kinds you want). This approach would probably be more self-documenting, if nothing else.Nice idea, but java.net.URL doesn't actually do much work at all. It basically takes the protocol part, looks up a handler for it, and delegates everything else to that. The handlers themselves are down in the sun packages (or whatever your Java impl is) and since there isn't one for the OPs protocol, he'd have to write and register his own anyway, which kind-of negates the entire purpose of leveraging it.
@OP: Paul's suggestion can still be of use. Apache, Codehaus and the like will have written their own protocol handlers, it's worth grabbing the source code for, say, Apache HttpClient, and seeing if they've got anything useful in there. Then again, who's to say that what's a valid URL for this 'norm' protocol, other than whoever designed the protocol?