When 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 .

Why can I instantiate an abstract class?

Abstract class, we have heard that abstract class are classes which can have abstract methods and it can't be instantiated. We cannot instantiate an abstract class in Java because it is abstract, it is not complete, hence it cannot be used.

Is abstract class must be instantiated?

An abstract class cannot be instantiated directly, i.e. the object of such class cannot be created directly using the new keyword. An abstract class can be instantiated either by a concrete subclass or by defining all the abstract method along with the new statement.

Can an abstract class be instantiated using the new keyword?

Abstract class can not be instantiated using new keyword.

How many instances of an abstract class can be instantiated?

What Is the Maximum Number of Instances That Can Be Created for an Abstract Class? A correct answer is an option (D) 0.

Why Abstract Classes cannot be instantiated in C# ?

Can Interfaces be instantiated?

An interface can't be instantiated directly. Its members are implemented by any class or struct that implements the interface. A class or struct can implement multiple interfaces.

Can we inherit abstract class?

An abstract class cannot be inherited by structures. It can contains constructors or destructors. It can implement functions with non-Abstract methods.

Can we create constructor of abstract class?

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 we declare class as static in Java?

We can declare a class static by using the static keyword. A class can be declared static only if it is a nested class. It does not require any reference of the outer class. The property of the static class is that it does not allows us to access the non-static members of the outer class.

Can we extend abstract class?

In Java, abstract means that the class can still be extended by other classes but that it can never be instantiated (turned into an object).

Can constructor be inherited?

Constructors are not members, so they are not inherited by subclasses, but the constructor of the superclass can be invoked from the subclass.

Can abstract class have zero abstract methods?

Yes, we can declare an abstract class with no abstract methods in Java. An abstract class means that hiding the implementation and showing the function definition to the user.

Can abstract class exist without abstract method?

And yes, you can declare abstract class without defining an abstract method in it. Once you declare a class abstract it indicates that the class is incomplete and, you cannot instantiate it. Hence, if you want to prevent instantiation of a class directly you can declare it abstract.

Can you instantiate an abstract class or an interface?

Those numbers denote the order in which those anonymous classes appear in the enclosing class. In one line you can say:- You can never instantiate an abstract class. That's the purpose of an abstract class.

Why can't we instantiate an abstract class in C#?

An abstract class cannot be instantiated because it may contain members that are abstract and have no implementation.

Can we instantiate abstract class in C++?

An abstract class is, conceptually, a class that cannot be instantiated and is usually implemented as a class that has one or more pure virtual (abstract) functions. A pure virtual function is one which must be overridden by any concrete (i.e., non-abstract) derived class.

Can constructor be static?

A static constructor is used to initialize any static data, or to perform a particular action that needs to be performed only once. It is called automatically before the first instance is created or any static members are referenced.

Can a class be private?

Yes, we can declare a class as private but these classes can be only inner or nested classes. We can't a top-level class as private because it would be completely useless as nothing would have access to it.

Can we inherit static class?

Static classes are sealed and therefore cannot be inherited. They cannot inherit from any class except Object. Static classes cannot contain an instance constructor. However, they can contain a static constructor.

Can we create immutable class in Java?

Immutable class in java means that once an object is created, we cannot change its content. In Java, all the wrapper classes (like Integer, Boolean, Byte, Short) and String class is immutable. We can create our own immutable class as well.

Can abstract class have private methods?

Abstract classes can have private methods. Interfaces can't. Abstract classes can have instance variables (these are inherited by child classes). Interfaces can't.

Can abstract class have parameters?

Yes, we can provide parameters to abstract method but it is must to provide same type of parameters to the implemented methods we wrote in the derived classes.

Why interface is used instead of abstract class?

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 inherit private class in Java?

A java private member cannot be inherited as it is available only to the declared java class. Since the private members cannot be inherited, there is no place for discussion on java runtime overloading or java overriding (polymorphism) features.

Can we declare abstract method as static?

Declaring abstract method static

If you declare a method in a class abstract to use it, you must override this method in the subclass. But, overriding is not possible with static methods. Therefore, an abstract method cannot be static.