How do I make a JAR from a .java file?

I was writing a simple program using a Java application (not application that has projects, but application within a project; .java) that has a single frame. Both of the files are .java so I can't write a manifest needed by the JAR.

The MyApp.java starts like a class with package, imports then public class MyApp and has a main function, but it's still .java file! I'm writing it in JDeveloper 11g if it helps.

Any ideas how to make a JAR from these files?