Can you instantiate interface

By using interfaces, you can, for example, include behavior from multiple sources in a class. That capability is important in C because the language doesn't support multiple inheritance of classes.

In addition, you must use an interface if you want to simulate inheritance for structs, because they can't actually inherit from another struct or class. You define an interface by using the interface keyword as the following example shows. The name of an interface must be a valid C identifier name.

By convention, interface names begin with a capital I. A class or struct can implement multiple interfaces, but a class can only inherit from a single class. Interfaces can contain instance methods, properties, events, indexers, or any combination of those four member types.

Interfaces may contain static constructors, fields, constants, or operators. An interface can't contain instance fields, instance constructors, or finalizers. Interface members are public by default, and you can explicitly specify accessibility modifiers, such as public , protected , internal , private , protected internal , or private protected. A private member must have a default implementation.

To implement an interface member, the corresponding member of the implementing class must be public, non-static, and have the same name and signature as the interface member. When a class or struct implements an interface, the class or struct must provide an implementation for all of the members that the interface declares but doesn't provide a default implementation for.

However, if a base class implements an interface, any class that's derived from the base class inherits that implementation. You use this class via its interface, without even knowing the class name. That's what interfaces are for.

SharedPreferences is an interface implemented in Context. What you see here is an example of abstracting towards an interface: by defining your pref variable as an interface you allow for easier code changes your current class is now loosely coupled with the Context class instead of putting a direct link towards it.

The object returned by Context. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams?

Collectives on Stack Overflow. Learn more. Can you instantiate an Interface in Java [duplicate] Ask Question. Asked 8 years, 7 months ago. I would have guessed that the syntax for doing this would look something like this, but this goofy because it's not really an anonymous class:.

Note that anonymous inner classes can either extend a class OR can implement only one interface. Here's an example of an anonymous class that extends a class notice that it does not include the 'extends' keyword :. You are only referring the Dog instance to it. In java we can take the super class reference.

This is a case of polymorphism, It looks like you are creating 'Animal' object but it is not. You are creating 'Dog' object which is calculated on run time. Interface can not be instantiated directly but can be used as type by upcasting its subclass. You can also use anonymous class to instantiate an object as 'Animal' type. The interface Animal is not be intantiated but be implemented by Dog. And a Dog is intantiated. The object type Dog is concrete and can be instantiated.

In this case, as long as Dog hasanimal point to Dog. The Interface Animal acts as the data type to the class Dog. You're actually instantiating the Dog class not the interface or it's data type. The whole idea is that in the table above you can put 10 animals of different types. The only conditions for this is that all the animals entering the Zoo must implement the interface Animal. You can't instantiate an interface. The functionality can be considered similar to that of an abstract class.

You can have a reference to the interface but you don't create an object of interface. If you do something like this Here it is just referencing to the interface but instantiation is done by the class only. What have you done is type casting. You have created an instance of class dog and has type caste it to interface animal.

It is an example of runtime polymorphosim. But yes an interface can be implemented and I have reached here while searching for this.

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