Can constructor be extended?

Asked By: Momath Imgraben | Last Updated: 12th February, 2020
Category: technology and computing programming languages
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Calling Constructors in Superclasses
In Java a class can extend another class. When a class extends another class it is also said to "inherit" from the class it extends. The class that extends is called the subclass, and the class being extended is called the superclass.

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Subsequently, one may also ask, can we extend constructor?

a constructor cannot be overridden. a constructor cannot be called with an object but method can be called. To call a constructor, an object must be created. in case of methods, we say, the "subclass method can call super class method".

Beside above, can we inherit a constructor? Constructors are not members of classes and only members are inherited. You cannot inherit a constructor. That is, you cannot create a instance of a subclass using a constructor of one of it's superclasses.

Similarly, it is asked, why constructor is not overridden?

Constructor Overriding is never possible in Java. This is because, Constructor looks like a method but name should be as class name and no return value. Overriding means what we have declared in Super class, that exactly we have to declare in Sub class it is called Overriding.

Can we call subclass constructor from superclass constructor?

5 Answers. A constructor from a subclass can call constructors from the superclass, but they're not inherited as such. because there's no Sub(int) constructor. It may be helpful to think of constructors as uninherited static methods with an implicit parameter of the object being initialized.

39 Related Question Answers Found

Can constructor be static?

Constructor is NON-STATIC and it cannot be declared as static in java . Instance is created by 'new' operator and that need not to be initialized to call a constructor (as constructor initializes the object). A constructor is never called as object. constructor() like methods.

Can a constructor override?

a constructor cannot be overridden. a constructor cannot be called with an object but method can be called. To call a constructor, an object must be created. in method overriding, the super class method and subclass method should be of the same – same name, same return type and same parameter list.

Can constructor be private?

Yes, class can have a private constructor. It is needed as to disallow to access the constructor from other classes and remain it accessible within defined class. A singleton is a design pattern that allows only one instance of your class to be created, and this can be accomplished by using a private constructor.

Can 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.

Does constructor return any value?

No, constructor does not return any value. While declaring a constructor you will not have anything like return type. In general, Constructor is implicitly called at the time of instantiation. And it is not a method, its sole purpose is to initialize the instance variables.

Can we override static method?

Answer is, No, you can not override static method in Java, though you can declare method with same signature in sub class. It won't be overridden in exact sense, instead that is called method hiding. As per Java coding convention, static methods should be accessed by class name rather than object.

Why we Cannot override static method?

Static methods cannot be overridden because method overriding only occurs in the context of dynamic (i.e. runtime) lookup of methods. Static methods (by their name) are looked up statically (i.e. at compile-time). Method overriding happens in the type of subtype polymorphism that exists in languages like Java and C++.

How do you extend in Java?

To create a sub class (child) from a Java super class (parent), the keyword extends is used. You then follow the "extends" keyword with the parent class you want to extend. We want to create a sub class from the StudentResults class.

Can abstract class have constructor?

Yes, an abstract class can have a constructor in Java. You can either explicitly provide a constructor to abstract class or if you don't, the compiler will add default constructor of no argument in abstract class. This is true for all classes and it also applies to an abstract class.

Can you use both this () and super () in a constructor?

Both this() and super() are constructor calls. Constructor call must always be the first statement. So we can not have two statements as first statement, hence either we can call super() or we can call this() from the constructor, but not both.

How are this () and super () used with constructors?

How are this() and super() used with constructors? Constructors use this to refer to another constructor in the same class with a different parameter list. Constructors use super to invoke the superclass's constructor. If a constructor uses super, it must use it in the first line; otherwise, the compiler will complain.

What is construction overloading?

Constructor overloading is a concept of having more than one constructor with different parameters list, in such a way so that each constructor performs a different task.

Can an interface be final?

Making an interface final.
If you declare a class final cannot extend it. If you make a method final you cannot override it and, if you make a variable final you cannot modify it. If you make an interface final, you cannot implement its methods which defies the very purpose of the interfaces.

Can we override constructor in C#?

No, you can't override constructors. The concept makes no sense in C#, because constructors simply aren't invoked polymorphically. Constructors aren't inherited at all - but all constructors from a derived class must chain either to another constructor in the same class, or to one of the constructors in the base class.

What is Polymorphism in Java?

Polymorphism in Java is a concept by which we can perform a single action in different ways. We can perform polymorphism in java by method overloading and method overriding. If you overload a static method in Java, it is the example of compile time polymorphism. Here, we will focus on runtime polymorphism in java.

What is call override?

Method overriding, in object-oriented programming, is a language feature that allows a subclass or child class to provide a specific implementation of a method that is already provided by one of its superclasses or parent classes.

What is the return type of constructors?

Constructors in Java do not return anything explicitly. They do not have a return type, not even void. However, as the definition of Constructor goes, it is used to initialize an object of the class. So implicitly, they return the current instance of the class whose constructor it is.