Question: Can Abstract Class Have Constructor C++?

Can we extend abstract class?

Abstract classes are similar to interfaces.

You cannot instantiate them, and they may contain a mix of methods declared with or without an implementation.

In addition, you can extend only one class, whether or not it is abstract, whereas you can implement any number of interfaces..

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 make copy constructor private?

Yes, a copy constructor can be made private. When we make a copy constructor private in a class, objects of that class become non-copyable.

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.

Does a class need a constructor C++?

9 Answers. A class doesn’t need a constructor. A default constructor is not needed if the object doesn’t need initialization.

Can constructor be static?

No, we cannot define a static constructor in Java, If we are trying to define a constructor with the static keyword a compile-time error will occur. In general, static means class level. A constructor will be used to assign initial values for the instance variables.

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 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.

Does a constructor have a return type C++?

Constructors in C++ Constructor is a special member function of a class that initializes the object of the class. Constructor name is same as class name and it doesn’t have a return type. Lets take a simple example to understand the working of constructor.

Can abstract class be inherited?

Abstract Class But, if a class has at least one abstract method, then the class must be declared abstract. If a class is declared abstract, it cannot be instantiated. To use an abstract class, you have to inherit it from another class, provide implementations to the abstract methods in it.

Can constructor be overloaded?

Yes! Java supports constructor overloading. In constructor loading, we create multiple constructors with the same name but with different parameters types or with different no of parameters.

How many constructors can a class have in C++?

C++ allows more than one constructor. The other constructors must have different parameters. Additionally constructors which contain parameters which are given default values, must adhere to the restriction that not all parameters are given a default value.

Can a final class be abstract?

No, you cannot make an abstract class or method final in Java because the abstract and final are the mutual exclusive concept. … 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.

Can abstract class have body?

Java Abstract Method 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 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.

What happens if a user forgets to define a constructor inside a class?

Also if any user forgets to define init() function then no object will be initialized whereas if any constructor is not defined in any class the class provides a default constructor for initialization.

Can we override static method?

Can we Override static methods in java? We can declare static methods with same signature in subclass, but it is not considered overriding as there won’t be any run-time polymorphism. Hence the answer is ‘No’.

Why do we use constructor?

The purpose of constructor is to initialize the object of a class while the purpose of a method is to perform a task by executing java code. Constructors cannot be abstract, final, static and synchronised while methods can be. Constructors do not have return types while methods do.

Why does an abstract class have a constructor?

1) Abstract classes have constructors and those constructors are always invoked when a concrete subclass is instantiated. … 2) We know constructor are also used to initialize fields of a class. We also know that abstract classes may contain fields and sometimes they need to be initialized somehow by using constructor.

What happens if you keep a return type for a constructor?

Since constructor can only return the object to class, it’s implicitly done by java runtime and we are not supposed to add a return type to it. If we add a return type to a constructor, then it will become a method of the class. This is the way java runtime distinguish between a normal method and a constructor.

Why can’t a constructor be final?

No, a constructor can’t be made final. A final method cannot be overridden by any subclasses. … In other words, constructors cannot be inherited in Java therefore, there is no need to write final before constructors. Therefore, java does not allow final keyword before a constructor.