Question: Can An Abstract Class Be Empty?

Can you inherit an abstract class?

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 an abstract class extend concrete?

An abstract class always extends a concrete class ( java. lang. … If you want to instantiate it, you will have to subclass it with a concrete implementation of those abstract methods and instantiate it through the concrete class.

Can abstract class have all concrete methods?

An abstract class is a class that is declared abstract – it may or may not include abstract methods. They cannot be instantiated so if you have an abstract class with concrete methods then it can be subclassed and the subclass can then be instantiated.

Can an interface have a constructor?

No, you cannot have a constructor within an interface in Java. You can have only public, static, final variables and, public, abstract, methods as of Java7. From Java8 onwards interfaces allow default methods and static methods.

Can one abstract class extend another?

An abstract class can extend another abstract class. And any concrete subclasses must ensure that all abstract methods are implemented. Abstract classes can themselves have concrete implementations of methods. These methods are inherited just like a method in a non-abstract class.

What is the difference between inheritance and abstraction?

4 Answers. Inheritance is for inheriting properties and having some of its own as well. Abstract is to restrict from being instantiated.

Can abstract class have normal methods?

It can have abstract methods(methods without body) as well as concrete methods (regular methods with body). A normal class(non-abstract class) cannot have abstract methods. … An abstract class can not be instantiated, which means you are not allowed to create an object of it.

Can abstract class have static methods?

Can an abstract class have static methods? Yes, abstract class can have Static Methods. The reason for this is Static methods do not work on the instance of the class, they are directly associated with the class itself.

Can we have abstract class 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.

What is the benefit of making an empty abstract method in a base class?

It allows you to add abstract methods to your superclass (and implementations to the subclasses) later, without affecting any existing clients. The abstract keyword works even if the non-leaf class does not currently have any abstract methods. An abstract class can have abstract methods and “concrete” methods.

Can a data field be declared abstract?

Abstract classes are similar to interfaces. You cannot instantiate them, and they may contain a mix of methods declared with or without an implementation. However, with abstract classes, you can declare fields that are not static and final, and define public, protected, and private concrete methods.

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 do we need 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 abstract class have constructors?

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 method have body?

Abstract methods means there is no default implementation for it and an implementing class will provide the details. So, it’s exactly as the error states: your abstract method can not have a body. The reason you would do something like this is if multiple objects can share some behavior, but not all behavior.