How to construct a relative path in Java from two absolute paths (or URLs)?

Question

Given two absolute paths, e.g.

/var/data/stuff/xyz.dat
/var/data

How can one create a relative path that uses the second path as its base?

Answer 1

Psuedo-code:

1. Split the strings by the path seperator ("/")
2. Find the greatest common path by iterating thru the result of the split string (so you'd end up with "/var/data" or "/a" in your two examples)
3. return "." + whicheverPathIsLonger.substring(commonPath.length);