Quick Answer: Can Abstract Class Have Constructor In CPP?

Why does an abstract class have a constructor?

Abstract classes require constructors to enforce a design contract using which objects can be initialized.

Constructor can be used to setting up an attribute of the base class.

This attribute will be available in subclass by inheritance.

Before using this attribute, using the constructor it can be initialized..

Can constructors be virtual in C++?

In C++, the constructor cannot be virtual, because when a constructor of a class is executed there is no virtual table in the memory, means no virtual pointer defined yet. So, the constructor should always be non-virtual.

Does an abstract class have a 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.

Can abstract class have body?

A concrete class is a subclass of an abstract class, which implements all its abstract method. Abstract methods cannot have body. Abstract class can have static fields and static method, like other classes. An abstract class cannot be declared as final.

Can you override static methods?

Static methods cannot be overridden because they are not dispatched on the object instance at runtime. The compiler decides which method gets called. Static methods can be overloaded (meaning that you can have the same method name for several methods as long as they have different parameter types).

Can a constructor be private?

Yes, we can declare a constructor as private. If we declare a constructor as private we are not able to create an object of a class. We can use this private constructor in the Singleton Design Pattern.

Can we override constructor?

Constructor looks like method but it is not. It does not have a return type and its name is same as the class name. But, a constructor cannot be overridden. If you try to write a super class’s constructor in the sub class compiler treats it as a method and expects a return type and generates a compile time error.

Can abstract class have private constructor?

Some classes serve only as holders for static fields/methods and do not want to be either instantiated or subclassed. … There is another use case, quite rare though: you can have an abstract class with only private constructors that contains its own subclasses as nested classes.

What is difference between interface and abstract class?

Main difference is methods of a Java interface are implicitly abstract and cannot have implementations. … Variables declared in a Java interface is by default final. An abstract class may contain non-final variables. Members of a Java interface are public by default.

Can constructor be static?

A static constructor does not take access modifiers or have parameters. A class or struct can only have one static constructor. Static constructors cannot be inherited or overloaded. A static constructor cannot be called directly and is only meant to be called by the common language runtime (CLR).

Why can’t a constructor be final?

A constructor is never inherited to an another class so it doesn’t need to be marked final. Hey, The constructor cannot be final because the constructor cannot be inherited and in constructor values are initialized to the variable so by this variables changes every time and yes it cannot be inherited.

Which is better abstract class or interface?

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 we declare abstract class as static?

Yes, of course you can define the static method in abstract class. you can call that static method by using abstract class,or by using child class who extends the abstract class. Also you can able to call static method through child class instance/object.

Can we declare abstract class as final?

In short, an abstract class cannot be final in Java, using both abstract and final modifier with a class is illegal in Java. … An abstract method must be overridden to be useful and called but when you make the abstract method final it cannot be overridden in Java, hence there would be no way to use that method.