Can a class have nested interface?

Yes, if we define a class inside the interface, the Java compiler creates a static nested class.

Can you cast an interface to a class?

Yes, you can. If you implement an interface and provide body to its methods from a class. You can hold object of the that class using the reference variable of the interface i.e. cast an object reference to an interface reference.

How do you define an interface in Java?

An Interface in Java programming language is defined as an abstract type used to specify the behavior of a class. An interface in Java is a blueprint of a class. A Java interface contains static constants and abstract methods. The interface in Java is a mechanism to achieve abstraction.

Can we have interface inside interface?

Yes, we can do it. The definition of the nested interface in java is as follows: A nested interface is any interface whose declaration occurs within the body of another class or interface. A top-level interface is an interface that is not a nested interface.

Can we create object of interface in Java?

Like abstract classes, interfaces cannot be used to create objects (in the example above, it is not possible to create an “Animal” object in the MyMainClass) Interface methods do not have a body – the body is provided by the “implement” class. On implementation of an interface, you must override all of its methods.

Can you instantiate an interface?

An interface can’t be instantiated directly. Its members are implemented by any class or struct that implements the interface. A class or struct can implement multiple interfaces.

Can we have object of interface?

No, you cannot instantiate an interface. Generally, it contains abstract methods (except default and static methods introduced in Java8), which are incomplete.

Can an interface extend a class?

Defining an Interface An interface can extend other interfaces, just as a class subclass or extend another class. However, whereas a class can extend only one other class, an interface can extend any number of interfaces. The interface declaration includes a comma-separated list of all the interfaces that it extends.

What is the difference between a class and an interface?

A class describes the attributes and behaviors of an object. An interface contains behaviors that a class implements. A class may contain abstract methods, concrete methods. An interface contains only abstract methods.