How was this code tested? The substring will return in an empty string (as substring endIndex is exclusive, or as others say it, the indices are "between" the letters; therefore `substring(x,x)` will always be empty), and String#substring throws NumberFormatException when called on an empty string. I don't have any experience with Android development and its API, though, so in the unlikely case that `Build.VERSION.RELEASE` is not a `(java.lang.)String`, please ignore this comment. :)