New method to check whether the specified path points to a valid audio file.
Removed code smells.
Formatted code.
Added a functional interface for a function which accepts three arguments.
Method to pick a random element from a list.
Removed code smell.
Generic methods to write/read a collection or a map to/from an XML file.
Added setter for first and second and constructor for empty pair.
Java doc corrected.
Documentation and formatting.