"Could not find the main class" error when running jar exported by Eclipse
I have a java project that works perfectly fine when running it from within Eclipse. When I try to export it to either a "JAR file" or "Runnable JAR file" the .jar file is created, but when I double click on it to try to run the program it gives me an error that says
"Could not find the main class: package.MainClassName. Program will exit."
As I mentioned, I tried exporting to both JAR options, I specified the correct class that the main method is in, and when I look through the actual files in the .jar file everything seems to be in order -- the manifest looks something like:
Manifest-Version: 1.0
Main-Class: package.MainClassName
(blank line)
and is in the META-INF folder. There is a folder with my package name, which contains all the .class files, including the class that contains the main method. A few image and text files that I use also appear in the jar file.
The actual program isn't anything too complicated -- it's a simple "snake" game using Swing (plus the code all works when run from inside Eclipse).
Any ideas what is causing this error and how I can fix it? Let me know if there's any other information I should provide.
Answer
Verify that you can start your application like that:
java -cp myjarfile.jar snake.Controller
I just read when I double click on it - this sounds like a configuration issue with your operating system. You're double-clicking the file on a windows explorer window? Try to run it from a console/terminal with the command
java -jar myjarfile.jar
Further Reading
The manifest has to end with a new line. Please check your file, a missing new line will cause trouble.