Can You Instantiate An Interface?

Can we declare interface as final?

If you make an interface final, you cannot implement its methods which defies the very purpose of the interfaces.

Therefore, you cannot make an interface final in Java.

Still if you try to do so, a compile time exception is generated saying “illegal combination of modifiers − interface and final”..

Why can’t we instantiate an interface?

You can’t instantiate an interface or an abstract class because it would defy the object oriented model. Interfaces represent contracts – the promise that the implementer of an interface will be able to do all these things, fulfill the contract.

Can you declare a constructor inside an interface if not why?

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.

Can you instantiate an abstract class?

Abstract classes cannot be instantiated, but they can be subclassed. When an abstract class is subclassed, the subclass usually provides implementations for all of the abstract methods in its parent class. However, if it does not, then the subclass must also be declared abstract .

Can a class instantiate itself?

so by line 1, class is both loaded and initialized and hence there is no problem in instantiating an instance of class in itself. But if your code is like this, … class Test { public static void main(String[] args) { Test test = new Test(); } } In the above code creating an instance won’t call main again.

Why can’t you instantiate an abstract class?

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. You CAN instantiate an abstract class. You only need to provide a concrete subclass.