What is the relationship between a package and its subpackage in Java? [duplicate]

Answer 1

No, there's no relation between odp.proj and odp.proj.subpackage from the Java language perspective.

For code, odp.proj.subpackage would reside in a sub directory of odp.proj, and some tools and IDE's might group them together in a UI, but regarding language access control, or other langage feature there's no relation.

Java does not have the concept of a subpackage, so odp.proj.subpackage and odp.proj are as different from each other as any other differently named packages.

Answer 2

Java has no concept of subpackages.

Beyond organization, packages define the accessibility of methods/fields with the protected and "package" (blank) modifiers, which allows same-class and same-package access. However, this same-package access does not include subpackage classes as well.

Answer 3

Usually if a package name contains the "internal" word, than the user should not use it directly, because it is not guarantieed, that those packages will be present in the future releases. This is only a naming convention, but still works as a workaround.

Answer 4

Short answer

The exact feature you are looking for doesn't exist.

Long Answer

They considered doing it for Java 1.7, but the case is dormant.

As far as what's actually real, there is no relationship at all between odp.proj and odp.proj.subpackage other than a directory structure, the protected keyword and things like import odp.proj.*; - except that statement doesn't get any classes from odp.proj.subpackage

One way to approach what you want is to release an API specification for what you want to expose and leave the rest undocumented or privately documented. Possibly you could even obfuscate the private classes in each release using something like ProGuard.