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Can an interface have inner class?
Yes, you can define a class inside an interface. In general, if the methods of the interface use this class and if we are not using it anywhere else we will declare a class within an interface.
Why is a member class of an interface not considered as an inner class?
A member class of an interface is implicitly static (§9.5) so is never considered to be an inner class. It is a compile-time error if an inner class declares a static initializer (§8.7). An inner class may inherit static members that are not constant variables even though it cannot declare them.
What is contract interface?
An interface is a contract that guarantees to a client how a class or struct will behave. When a class implements an interface, it must implement all the methods of that interface; in effect the class says “I agree to fulfill the contract defined by this interface.”
How is an interface contract different from a class object?
An interface defines a set of methods that all implementing classes must support. The interface itself is the contract that you define for the implementing classes. It just says that any class that implements the interface, must have that interface’s set of public methods.
Can a class in an interface have an inner class?
Using your narrowed definition, interfaces can not have inner classes. You can omit the static modifier of an interface’s nested class but still, it’s a nested class, not an inner class. This answer is wrong. Interfaces can have static nested classes but not inner classes.
Can a contract checker be nested in an interface?
I’ve seen it used to put some kind of “contract checker” directly in the interface definition (well, in the class nested in the interface, that can have static methods, contrarily to the interface itself, which can’t). Looking like this if I recall correctly.
Which is an example of an inner class?
Since classes may be defined as inner classes to interfaces, we can use inner classes to provide default or alternate implementations for interfaces. An Example In the following example we see the definition of a Stack interface with the usual push and pop operations.