Can A Superclass Object Be Instantiated As A Subclass Object?

When a subclass is instantiated, the superclass _____________ constructor is executed first. When a subclass is instantiated, what is instantiated first? The superclass default constructor. Think of this as “The parent has to be created before the child is created.”

When an object that is a member of a subclass is instantiated which Constructors is called?

A subclass can have its own private data members, so a subclass can also have its own constructors. … Thus, when a subclass object is instantiated the subclass object must also automatically execute one of the constructors of the superclass. To call a superclass constructor the super keyword is used.

Can a constructor be final?

No, a constructor can’t be made final. A final method cannot be overridden by any subclasses. … But, in inheritance sub class inherits the members of a super class except constructors. In other words, constructors cannot be inherited in Java therefore, there is no need to write final before constructors.

What happens when this is used in a constructor’s body to call another constructor?

no-argument constructor. 8.5 Q4: What happens when this is used in a constructor’s body to call another constructor of the same class if that call is not the first statement in the constructor? a. a. A compilation error occurs.

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.

What is super () in Java?

The super keyword in Java is a reference variable which is used to refer immediate parent class object. Whenever you create the instance of subclass, an instance of parent class is created implicitly which is referred by super reference variable. … super can be used to invoke immediate parent class method.

Does a superclass need a constructor?

A subclass needs a constructor if the superclass does not have a default constructor (or has one that is not accessible to the subclass). If the subclass has no constructor at all, the compiler will automatically create a public constructor that simply calls through to the default constructor of the superclass.

When an object of a subclass is instantiated a superclass constructor is called?

When a subclass is instantiated, instantiate all the superclasses are instantiated at the same time. Here, the initialization of superclass attributes is ensured by the call of the superclass constructors, as described in Inheritance and Constructors.

Can constructor be private?

Yes. Class can have private constructor. Even abstract class can have private constructor. By making constructor private, we prevent the class from being instantiated as well as subclassing of that class.

Is overriding possible in Java?

Can we override java main method? No, because the main is a static method.

Is an object a subclass?

is that object is (computing) in object-oriented programming, an instantiation of a class or structure while subclass is (computing) in object-oriented programming, an object class derived from another class (its superclass) from which it inherits a base set of properties and methods.

Can an object be a subclass of another object?

2. Can an object be a subclass of another object? A. Yes—as long as single inheritance is followed.

What is it called when I declare an object of a superclass and assign an object of a subclass to it?

Therefore, if you assign an object of the subclass to the reference variable of the superclass then the subclass object is converted into the type of superclass and this process is termed as widening (in terms of references).

What does super () do?

The super() in Java is a reference variable that is used to refer parent class constructors. super can be used to call parent class’ variables and methods. super() can be used to call parent class’ constructors only.

Is Super called automatically Java?

If you don’t write an explicit call to the super() constructor, Java automatically inserts one in your constructor. The compiler automatically inserts superclass constructor calls in both constructors. … However, when the Child class constructor is modified to call its superclass constructor, there’s a problem.

What is the difference between this () and super ()?

Difference between super() and this() in java. super() as well as this() both are used to make constructor calls. super() is used to call Base class’s constructor(i.e, Parent’s class) while this() is used to call current class’s constructor. super() is use to call Base class’s(Parent class’s) constructor.

Can main method be overloaded?

Yes, We can overload the main method in java but JVM only calls the original main method, it will never call our overloaded main method. Output: … So, to execute overloaded methods of main, we must call them from the original main method.

How can parameterized constructor be overloaded?

Using this() in constructor overloading

this() reference can be used during constructor overloading to call default constructor implicitly from parameterized constructor. Please note, this() should be the first statement inside a constructor.

Can destructors be overloaded?

Answer: No, we cannot overload a destructor of a class in C++ programming. … Destructor in C++ neither takes any parameters nor does it return anything. So, multiple destructor with different signatures are not possible in a class. Hence, overloading is also not possible.

Can we use this () and super () in a method?

both this() and super() can not be used together in constructor. this() is used to call default constructor of same class.it should be first statement inside constructor. super() is used to call default constructor of base class.it should be first statement inside constructor.

Can a constructor call another constructor?

Constructor chaining is the process of calling one constructor from another constructor with respect to current object. Constructor chaining can be done in two ways: Within same class: It can be done using this() keyword for constructors in same class.

Can a class constructor be called more than once?

Constructor is called automatically when we create an object using new keyword. It is called only once for an object at the time of object creation and hence, we cannot invoke the constructor again for an object after it is created.


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