I've been searching for a way to have users set my program as the default to open files for awhile and found nothing. I have a program that is supposed to be universal for Mac, Windows and Linux, so I don't want to use a method that only works with one OS. So how can I give users the ability to set a Java app as the default file opener? Would I use the Desktop class?
No Java does not support this. You would have to write a small app for every OS that you want to support in its native language (c++, objective c, etc.) that would simply launch your java app whenever it is opened. You can then set that app as the default program.