how to create a java jar file with only subfolder's content?

Now I am in a temp folder in my dos console. there is a classes folder inside the temp folder. that classes folder contains all my classes started with 开发者_运维知识库com.companyName.app folder structure. I use "jar cf project.jar classes\*" to create the jar file but it starts with classes folder. I don't want the classes folder. The top level folder I expected is the com. How can do it? or I have to cd to classes folder to do that? thanks,

jar cf project.jar -C classes .