How to create jar file with package structure?

You need to start creating the JAR at the root of the files.

So, for instance:

jar cvf program.jar -C path/to/classes .

That assumes that path/to/classes contains the com directory.

FYI, these days it is relatively uncommon for most people to use the jar command directly, as they will use a build tool such as Ant or Maven to take care of that (and other aspects of the build). It is well worth the effort of allowing one of those tools to take care of all aspects of your build, and it's even easier with a good IDE to help write the build.xml (Ant) or pom.xml (Maven).

You want

$ jar cvf asd.jar .

to specify the directory (e.g. .) to jar from. That will maintain your folder structure within the jar file.