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Can interfaces be modified?
An interface can extend other interfaces, just as a class subclass or extend another class.
Why should you program to an interface and not an implementation?
But the reason for it? Simple: “Coding to interfaces, not implementation.” If the object complies with the interface, your tests will behave the same way as the mocks. It also works when creating tests that depend on code done by another person or team and you do not have the real object yet.
Is it possible to change the value of an interface field explain?
No, we can’t change the value of an interface field because interface fields are final and static by default.
What does ” program to interfaces, not implementations ” mean?
The statement you mentioned says that if you plan to reuse some part of an algorithm (or more generally a program), you should create interfaces and rely on them, so you might change the concrete implementation any time without changing other objects if you use the declared interface.
When do you need to reflect changes in an interface?
Just think about it, if you have defined a public interface and a bunch of down stream components consume it, any changes you make to the interface immediately need to be reflected by the class consumers, no exceptions.
Why do you postpone changes to an interface?
This feature allows you to postpone downstream change because the interface itself holds a concrete method or property it can fall back on. Take this example interface: Implemented here: I can now make changes to the interface without immediately modifying the previous class:
What happens when you add a member to an interface?
If you provide an implementation, adding a new member to an existing interface won’t necessarily result in compile failures in downstream assemblies. However, not all languages support default interface members (DIMs). Also, in some scenarios, the runtime can’t decide which default interface member to invoke.