Thread: Eclipse - "Could not find or load main class conditionalDemo"

OK I've been playing around, following some tutorials... I had to classes in a project that seemed to conflict, I'm not sure why. Basically when I ran one it gave me the result of the other...

So I created a new Java project, deleted one of the classes and pasted it into the new project... However it still didn't work, and basically now when I try to run the program I get this error :



I've not encountered this before, I'm sure it's fairly simple but I don't really know how to solve it.

I'm seen some post's saying to restate the files path, clean bin and stuff.... I've not encountered this before though so I wouldn't be too sure what to do if I did know which one to try!

cheers

--- Update ---

I think I've still got the file on my computer :



I'm not sure though.... Should this be deleted?

There is more than one odd about the graphic you posted, but the main odd thing is that the names don't match. The black line says it was running ConditionalDemo1, but the error message says it was looking for ConditionalDemo. Is the class name the same as the file name without the '.java'? Apparently not. Fix that and report back.

Responding to your update, it shouldn't matter.

Hi Greg - here's a screen shot, I've changed the class name to 'ConditionalDemo' (is this what you meant?)



--- Update ---

I won't actually let me run any programs now, just returns that error each time

The project's name is ConditionalDemo2. That's fine.

The filename is ConditionalDemo.java, and the class' name is ConditionalDemo. so those are as they should be.

The black writing in the Console view says Eclipse was trying to run ConditionalDemo1. That doesn't match the code or project structure.

Click on the package name, ConditionalDemo2, in the Project Explorer pane in the left pane. Select F5 (Refresh). Then right click on the class name, ConditionalDemo, in the Project Explorer, select "Run as" then "Java Application".

That should fix your setup and run the program. If not, post any new errors or unexpected behaviors.

Ah bingo, that's weird... It returns this error for every program (in this workspace) so each time I open a program I just do this?

I've just tested it and it works... Closed Eclipse and re-opened it and the projects that I had done that to stayed 'worked'...

Is there some kind of 'cache' that I should clear?



Cheers though greg!

Not that I know of. Eclipse keeps the details of the workspace in an xml file or similar in each workspace, and when that file becomes corrupted either on purpose or by accident, there's no way to edit it or fix it that I'm aware of. Opening and closing is probably a good start, but if it becomes hopelessly muddled, one might have to move the code to a new workspace. The code should survive.

Next time, either copy and past the source code into a class of the same name in the new workspace/project OR use the import feature to import existing projects into workspace. There are several ways to do it right, probably just as many ways to do it wrong, and you'll figure them all out if you keep at it long enough. You should also figure out how to recover from the wrong ways, though sometimes it's easiest just to start over and use one of the right ways.

I think I confused it by dragging a file from one package to another... Will be reading about the import / export feature next time! cheers

That will normally work as long as you do it using the Package Explorer, and you allow Eclipse to "update references." I think that's what it's called. Eclipse gives you the option to skip that step, and if you do, you're likely to end up with a confused workspace that you'll have to clean up manually. That's what you just did, and it wasn't that big of a deal.

Also, the "Run" button and corresponding run list will become confused at times. When selected, the run button attempts to run the currently selected class, but if the currently selected class doesn't contain a main() method, it will run the last class run at the top of the run list. If the workspace becomes muddled, the run list may not be correct anymore, containing a class that no longer exists or whose name has changed, etc. Running the desired class may require right clicking the class and selecting Run As as you did earlier.

The good news is that you have to work incredibly hard to confuse Eclipse so badly that source files are lost.