防止方法在另一个包中被调用/覆盖

Question

I have this abstract class myapi.MyAbstract which is extended by client bundles.

package myclientbundle;

import myapi.MyAbstract;

public class MyClass extends MyAbstract {
    // Implementation
}

I need to add a non-API method at myapi.MyAbstract , but I can't find a way of doing that. That method is intended to be called only from inside my API bundle.

The closest I've got to the solution was put the method as default inside an internal interface and change myapi.MyAbstract to implement MyInternalInterface . So that, MyClass would inherit that method and it wouldn't be able to being called from outside of the API bundle. But it doesn't prevent of being overridden at client bundle.

Is there another way of doing that?

Answer 1

EDIT

I understand MyAbstract and MyClass are in different packages. (If they would be in the same package check here for package-private access level).

The interface you define the method on will need to have at least protected visibility, otherwise your class MyClass , which is in another package cannot read it.

A method on an interface is by definition public and cannot be final. Therefore a default method on an interface is visible to all classes and can be overriden.

You could do like this:

public abstract class MyAbstract {
    protected final void foo() {}
}

public class MyClass extends MyAbstract {
}

The foo method will be visible by all classes extending from MyAbstract , but the method cannot be overriden anymore, because it has been marked final

Answer 2

If your interface has different scoped method, you should ask yourself if you do not violate the Single Responsibility principle. For example, you could create 2 API Interface (different packages or bundles) if they need both to be accessed from elsewhere.

However, if it's only for internal usage, you could create a second interface, more specific, in the implementation bundle/not exported package.

For example : MyAbstract (API) <--- MySpecificAbstract (Interface, but in IMPL) <------- MyClass (IMPL).