IDE Eclipse Exporting Problem

hi, okay I am make a mini 2d game engine just for self learning purposes anyway when i try and export it as a runnable jar it exports without any errors and when i click on it to run it, it doesn't run. there isnt anything wrong with my code because it works fine in eclipse when click the run or debug button. i used package required libraries into generated jar also and im pretty sure i have the right launch config. all my resources are in the build path, i have no idea why its not launching. can you think of any reason why it wont launch ? thanks :)

Thread moved from 'What's wrong with my code', as you've posted no code.

Run the jar via the command line (java -jar myjar.jar), you can then see what - if any - exceptions may be thrown to help resolve the problem.

sorry i just didnt know where to put it but thanks

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i love you man <3 i have been trying to figure it out for ages