Can abstract class have instance?

Can abstract class have instance?

A Java abstract class is a class which cannot be instantiated, meaning you cannot create new instances of an abstract class. The purpose of an abstract class is to function as a base for subclasses.

Can instance variables be declared in abstract classes?

Abstract classes can have instance variables (these are inherited by child classes). Interfaces can’t. Finally, a concrete class can only extend one class (abstract or otherwise). However, a concrete class can implement many interfaces.

Can you construct an instance of an abstract class directly?

You can’t directly instantiate an abstract class.

Can I create an instance of abstract class in Java?

No, we can’t create an object of an abstract class. The reference variable is used to refer to the objects of derived classes (subclasses of abstract class). An abstract class means hiding the implementation and showing the function definition to the user is known as Abstract class.

Can abstract class be empty?

The key is that you can extend from only one abstract class, while you can implement more interfaces. Apparently the “empty abstract class” design desicion was made so that it prevents the implementing class from extending from another classes.

Can abstract class have multiple constructor?

Yes, an abstract class can have a constructor in Java. The compiler automatically adds the default constructor in every class either it is an abstract class or concrete class.

Can we declare abstract class as final?

Yes, there may be “final” methods in “abstract” class. But, any “abstract” method in the class can’t be declared final. It will give “illegal combination of modifiers: abstract and final” error. Here is the working example of the implementation.

Why are abstract classes not instantiated in Java?

This will create a concrete class behind the scenes which will be used. If your abstract class don’t contain any abstract method, you can not create instance of it. By making a class abstract, you told compiler that, it’s incomplete and should not be instantiated. Java compiler will throw error, when a code tries to instantiate abstract class.

Why can’t we create an object for 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.

Why are Java interfaces cannot have constructor but abstract classes can?

In order to call a method, we need to create an object, since the methods inside the interface by default public abstract which means the method inside the interface doesn’t have the body. Therefore, there is no need for calling the method in the interface.

Can a non abstract class be inherited from an abstract class?

An abstract class may contain abstract methods and accessors. It is not possible to modify an abstract class with the sealed modifier, which means that the class cannot be inherited. A non-abstract class derived from an abstract class must include actual implementations of all inherited abstract methods and accessors. Priyanka Jadhav.