Generalize 3 enums into one type

Question

I'm writing a Java program that does some calculations on files. The program supports 3 types of files (documents, images, videos) with each type allowing only few formats:

enum DocType {     pdf, doc, docx, xls, xlsx, ppt, pptx }  enum ImageType {     bmp, jpg, png, gif, ico }  enum VideoType {     avi, mpg, mp4, wmv, mov, flv, swf, mkv } 

In some point in my program, I would like to hold the file extension regardless of the file type, this means that I'd like to be able to do any of the following assignments:

FileType fileExt = DocType.doc FileType fileExt = ImageType.jpg FileType fileExt = VideoType.mp4 

How can I accomplish that behavior in Java? I know enums cannot extend other enums so basically the elegant solution is not possible.

Thanks

Answer 1

You can declare an interface that governs them all

interface FileType{ }  enum DocType implements FileType{  PDF // yes, uppercase for constants  ... }  enum ImageType implements FileType{  .... } 

And then you can declare variables of type FileType

FileType file = DocType.PDF;