Java large datastructure for storing a matrix

Question

I need to store a 2d matrix containing zip codes and the distance in km between each one of them. My client has an application that calculates the distances which are then s

Answer 1

I upvoted Chi's and Benjamin's answers, because they're telling you what you need to do, but while I'm here, I'd like to stress that using the hashcode of the two strings directly will get you into trouble. You're likely to run into the problem of hash collisions.

This would not be a problem if you were concatenating the two strings (being careful to use a delimiter which cannot appear in the place designators), and letting HashMap do its magic, but the method you suggested, using the hashcodes for the two strings as a key, that's going to get you into trouble.