I'd try something like this:
1. String.split() to split at the '+' character. Store each
string separately (duh :-) )
2. Use String.split() again, but this time split at the characters '(', ',' ' ' (space) and ')'. This should give you a String array of the individual numbers. You will (I think) get an empty array if there were no numbers (ie '()')
3. Create int arrays of the same lenght as the String arrays you got in step 2.
4. Use Integer.parseInt() to convert strings to integers, and store in the new int arrays.
The trickiest thing here is getting the regexps right when using String.split().
I find the biggest challenge in Java is knowing which methods to use, and when...the libraries are massive!
Hope that helps.
--Tim