extension : Java Glossary

In windows, the characters after the dot in a filename give you a clue what the file contains: e.g. something.html contains HTML (Hypertext Markup Language), *.txt is simple text, *.exe is an executable, *.java is Java source. Each of these extension is associated with a MIME (Multipurpose Internet Mail Extensions) type which is a long winded way of saying the same thing. You can associate given extensions with certain apps so that when you double click a file the corresponding program that knows how to deal with that file type is automatically launched with that file.

File offers no built-in way to get the extension or the filename without extension. Here is how you do it: