Quick Answer: Why Do We Need Abstract Class?

Can abstract class have constructor C++?

An abstract class can have constructor similar to normal class implementation.

In the case of the destructor, we can declare a pure virtual destructor..

What is difference between interface and abstract class?

Classes can implement multiple interfaces, but only one abstract class. Abstract classes can contain non-abstract methods. They can both have methods, variables, and neither one can be instantiated. All variables declared in an interface are final, while an abstract class may contain non-final variables.

Why do we need abstract class in C++?

The purpose of an abstract class (often referred to as an ABC) is to provide an appropriate base class from which other classes can inherit. Abstract classes cannot be used to instantiate objects and serves only as an interface. Attempting to instantiate an object of an abstract class causes a compilation error.

Why do we use abstract class in OOP?

Declaring a class as abstract means that it cannot be directly instantiated, which means that an object cannot be created from it. That protects the code from being used incorrectly. Abstract classes require subclasses to further define attributes necessary for individual instantiation.

Why can’t we 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.

Which method Cannot be overridden?

A method declared final cannot be overridden. A method declared static cannot be overridden but can be re-declared. If a method cannot be inherited, then it cannot be overridden. A subclass within the same package as the instance’s superclass can override any superclass method that is not declared private or final.

Can abstract class have constructor?

Yes! Abstract classes can have constructors! Yes, when we define a class to be an Abstract Class it cannot be instantiated but that does not mean an Abstract class cannot have a constructor. Each abstract class must have a concrete subclass which will implement the abstract methods of that abstract class.

Why do we need abstract class in Java?

Abstract class in java can’t be instantiated. … Java Abstract class can implement interfaces without even providing the implementation of interface methods. Java Abstract class is used to provide common method implementation to all the subclasses or to provide default implementation.

Can we inherit abstract class?

An abstract class defines the identity of a class. An interface can inherit multiple interfaces but cannot inherit a class. An abstract class can inherit a class and multiple interfaces. … An abstract class can declare constructors and destructors.

Can we instantiate 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 abstract method have body?

Abstract methods means there is no default implementation for it and an implementing class will provide the details. So, it’s exactly as the error states: your abstract method can not have a body. The reason you would do something like this is if multiple objects can share some behavior, but not all behavior.