This is a pretty good website on regex to provide you with some guidance:
http://www.regular-expressions.info/
As to your specific question, break it down into parts.
What does this part match?
Now what does this part match?
It's pretty confusing when you try to look at it as a whole, but when you break it down into parts it's much simpler. You can
test your
patterns for matches using the java.util.regex.Matcher class.
example:
Hunter