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Java Forum / General / June 2007Understanding class access
Hello, let's say I'm writing a extension organized in packages such as: mycompany.mypackage.MyClass mycompany.mypackage.subpackage.MySubClass The people who are going to use my extension will extend MyClass. So I declare it to be public. But I don't want people to be able to access MySubClass, so I can't declare as public. But I want MyClass to be able to access MySubClass, and if I don't declare MySubClass to be public, the compiler complains that MySubClass is in a different package and must be public. (I hope I'm being clear here :-) Is there anyway that I can access MySubClass from MyClass, but make MySubClass invisible for packages outside mycompany.mypackage? Thank you in advance, André > let's say I'm writing a extension organized in packages such as: > > mycompany.mypackage.MyClass > mycompany.mypackage.subpackage.MySubClass > Is there anyway that I can access MySubClass from MyClass, but make > MySubClass invisible for packages outside mycompany.mypackage? No, because in fact, though the names look herarchical, your mycompany.mypackage.subpackage is outside of mycompany.mypackage. (As a side note, if MySubClass is a subclass of MyClass, then trying to access MySubClass from MyClass is a cyclic dependency anyway.) It's hard to suggest more than that without knowing why you don't want anyone outside of mycompany.mypackage to access MySubClass. Is it simply an organizational principle? If so, then you'll notice a lot of packages in the standard librari have "implementation" or "provider" subpackages, and just rely on documentation to say that others shouldn't use it. If it's a security issue, such as when running untrusted code in the VM, then you'll have to redesign a bit more than that.  SignatureChris Smith > Hello, > [quoted text clipped - 19 lines] > > André If you don't want MySubClass to be subclassed, declare it final -- that's what it's there for. > If you don't want MySubClass to be subclassed, declare it final -- > that's what it's there for. What I mean is: I don't want it to be accessed. André > > If you don't want MySubClass to be subclassed, declare it final -- > > that's what it's there for. > > What I mean is: I don't want it to be accessed. If you don't want it confusing people or "cluttering things up", just don't include the javadoc for mysubpackage in your released documentation bundle, or include in the package-info.html that it's a private subpackage of little interest to most users. If you really want to completely deny access to MySubclass except via MyClass, make it a private nested class of MyClass. >> If you don't want MySubClass to be subclassed, declare it final -- >> that's what it's there for. > > What I mean is: I don't want it to be accessed. Move it to the same package and declare it package-private. SignatureLew > Hello, > [quoted text clipped - 19 lines] > > André If you don't want MySubClass to be subclassed, declare it final -- that's what it's there for. Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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