In the tutorial I found out that jar files can be created in the following way:
jar cf jar-file input-file(s)
However, it was not clear wha
The Jar-file could contain any file you want, but to hold a Java-program you need at least the .class-files, so you have to include them. The Game-class you are talking about may be dependant on the other classes. You can check that: delete all .class-files and recompile only Game.java (javac Game.java). All other classes that are compiled are a dependency. All of these have to be included in the Jar-file, that your program can be run. The class-files generated, that have not a corresponding .java-file (i.e. your GameWindow$2$7.class) are inner anonymous classes, in your example a inner class of the class GameWindow. If other libraries are needed, these must be present on other computers, that your program can be run. But you can include the content of the other jars into your jar, so that all that is needed is bundled into one file.