Make file open with different program

"This is simply because you changed the default for that registered filetype, this is easy to change back.

In any explorer window (you can use that one you have open in the picture) go to:

Tools -> Folder Options -> ""File Types"" tab
Scroll down the list to find the .java extension
Highlight the .java selection.
Where it says ""Opens With:"", click the ""Change..."" button and choose JCreator."