Can I create an object of interface?

We can’t create instance(interface can’t be instantiated) of interface but we can make reference of it that refers to the Object of its implementing class. A class that implements interface must implements all the methods in interface. All the methods are public and abstract.

Why we can not create an object of abstract class or interface?

Because an abstract class is an incomplete class (incomplete in the sense it contains abstract methods without body and output) we cannot create an instance or object; the same way you say for an interface.

Can you cast an object to an interface?

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.

Why we Cannot create a constructor to an interface?

Constructor in an interface An Interface in Java doesn’t have a constructor because all data members in interfaces are public static final by default, they are constants (assign the values at the time of declaration). There are no data members in an interface to initialize them through the constructor.

Can we create object of abstract class and interface in Java?

You cannot create an object of abstract class or interface since they are incomplete class (interface is not even considered as a class.)

Can we create object for interface in Java?

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

Can a Java interface have constructors?

No, you cannot have a constructor within an interface in Java. You can have only public, static, final variables and, public, abstract, methods as of Java7. From Java8 onwards interfaces allow default methods and static methods.