How do you export multiple java files as a singular runnable jar file in Eclipse?

I have a project with 3 java files:
Title_Screen .java
Game_Screen .java
Game_Code .java

Game_Screen and Game_Code use OpenGL, and Title_Screen opens Game_Code which opens Game_Screen. In eclipse, the program works perfectly, but when I try to export it as a runnable jar file, no matter what I do, it always just exports Title_Screen.java. What am I doing wrong, and what steps do I have to take to export all three java files in one .jar file?

Edit: It seems to only happen to my program, perhaps it's something to do with the OpenGL libraries?

Edit 2: I removed the libraries from my program, same results as exporting it to a jar file. My actual problem is that I can't put in the libraries.

Edit 3: Problem resolved! All I had to do was use jarsplice to create my runnable jar, not Eclipse. Tutorial I used: https://www.youtube.com/watch?v=YqGUk84BmlQ

You can use the following command to build the jar and specify the main class entry point (Main).

jar cfe output.jar Main src/Repository/* src/util/*.class

you can write multiple files when creating the jar

jar cf Output.jar src/util/Main.class src/util/SubMain.class src/Repository/*

Or from eclipse

Put all your files in a folder in your Eclipse project and then:

1.Right click in your folder
2.Export
3.Java -> Runnable JAR File

What steps are you following to export it as runnable jar?
Are you able to run the jar file successfully?

Steps to export Runnable jar is :

1. Right click on project and select "Export" option.
2. Provide the destination path where the jar file needs to be store.
3. Export