Why Does Abstract Class Have Constructor?

Should an abstract class have a constructor?

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.

Hence we can have a constructor in abstract classes..

What is the main reason for using abstract classes?

The short answer: An abstract class allows you to create functionality that subclasses can implement or override. An interface only allows you to define functionality, not implement it. And whereas a class can extend only one abstract class, it can take advantage of multiple interfaces.

Can a constructor be abstract?

You can’t have an abstract constructor, as abstract means you need to provide the implementation for that at some point of time in your subclass. But you cannot override constructor. There will be no point in having an abstract constructor : Since the constructor needs to be of the same name as of class.

What is difference between abstract class and interface?

Abstract class can inherit another class using extends keyword and implement an interface. Interface can inherit only an inteface. Abstract class can be inherited using extends keyword. Interface can only be implemented using implements keyword.

Why do we need constructor in abstract class C#?

Answer: Yes, an abstract class can have a constructor. In general, a class constructor is used to initialize fields. Along the same lines, an abstract class constructor is used to initialize fields of the abstract class.

Why abstract classes Cannot be instantiated?

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.

Can I instantiate an abstract class C#?

An abstract class cannot be instantiated. … The sealed modifier prevents a class from being inherited and the abstract modifier requires a class to be inherited. A non-abstract class derived from an abstract class must include actual implementations of all inherited abstract methods and accessors.

Can abstract class have properties C#?

An abstract property declaration does not provide an implementation of the property accessors — it declares that the class supports properties, but leaves the accessor implementation to derived classes. The following example demonstrates how to implement the abstract properties inherited from a base class.

Can an abstract class be instantiated?

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 .

How do you implement an abstract class?

To create an abstract class, just use the abstract keyword before the class keyword, in the class declaration. You can observe that except abstract methods the Employee class is same as normal class in Java. The class is now abstract, but it still has three fields, seven methods, and one constructor.

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.

Can abstract class have body?

Abstract methods are declaration only and it will not have implementation. It will not have a method body. A Java class containing an abstract class must be declared as abstract class. An abstract method can only set a visibility modifier, one of public or protected.

Can we instantiate a class which does not have even single abstract methods but declared as abstract?

Yes we can have an abstract class without Abstract Methods as both are independent concepts. Declaring a class abstract means that it can not be instantiated on its own and can only be sub classed. Declaring a method abstract means that Method will be defined in the subclass.

Can’t instantiate abstract class with abstract methods?

A class that is derived from an abstract class cannot be instantiated unless all of its abstract methods are overridden. You may think that abstract methods can’t be implemented in the abstract base class. … Even if they are implemented, designers of subclasses will be forced to override the implementation.

Is abstract Cannot be instantiated Java interface?

You can’t instantiate an interface. The functionality can be considered similar to that of an abstract class. You can have a reference to the interface but you don’t create an object of interface. If you do something like this….