4. Files.   

A file is a sequential collection of related objects.

Java has many file manipulation routines. It lets you have files of characters (== text files) as well as files of arbitrary binary bit patterns (== non-text files). 



       Java Text Files.  

       Java Non-Text Files.
Surprise!!

Other languages have different ways of doing I/O, some more complex, some more flexible. Java is very good at I/O.