Hiding classes in a jar file

Question

Is it really impossible to hide some classes in a jar file?

I wanted not to allow direct instantiation of the classes to keep it more flexible. Only the factory (or

Answer 1

With standard classloaders and plain old jar files, this is not possible. OSGi has this concept of making visible only some packages to another bundle(i.e. separation of public api and internal implementation).

If you are using eclipse, you may enforce such rules with this

Answer 2

Obfuscation can help you somehow.