Abstract Class vs Interface In Java

Abstract classes and interfaces are two of the most important structural components of the Java programming language. This article will help you understand the difference between abstract classes and interfaces.

Java is widely regarded as one of developers’ most popular programming languages. Even though it is getting on in years and Python is becoming an increasingly popular alternative, Java’s consistency and popularity ensure that the programming language will continue to play an important role in software development for many years.

Programmers and developers interested in making the most of the features offered by Java should improve their familiarity with the language and its capabilities. This deeper comprehension works beautifully in tandem with advancing one’s skill level.

To accomplish this, we will now look at Java’s abstraction methods. Abstract classes and interfaces are two of the most important structural components of the Java programming language. This article will help you understand the difference between abstract classes and interfaces.

Let’s begin by defining some terms before we move on to discussing abstract class vs. interface.

What Exactly Is Abstract Class?

An abstract class is identified by the class declaration’s use of the word “abstract.” An abstract class, unlike a regular class, can have both abstract and concrete methods (a method without a body and a method with a body, respectively). We cannot make objects based on abstract classes because they cannot be instantiated. However, it is possible to have references to abstract classes by developing another class that extends the abstract class and implements methods.

A child’s newly created object can be used to call both abstract and regular methods. It can have constructors, and when a new instance of a class that inherits from it is made, the abstract class is the one that is called. In Java, it is possible to have an abstract class even if the abstract keyword is not used; however, these classes cannot be instantiated and can only be inherited; in addition, their methods can be final.

Reasons For Employing Abstract Class

  • Abstract classes are intended to provide the functionality to subclasses by default.
  • It serves as a model for upcoming classes that are more specific.
  • Assists in the creation of a standardised user interface for its subclasses.
  • Abstract classes make it possible to reuse code.

Use Cases For Abstract Classes

  • If we use the inheritance concept, an abstract class is a good option because it supplies derived classes with a common implementation of the base class.
  • If we want to declare members that are not accessible to the general public, we should use an abstract class. Every method in an interface needs to be accessible to the public.
  • If there is a possibility that new methods might be added in the future, then we should go with an abstract class. If we modify an interface by adding new methods, then all of the classes that use that interface will need to be updated to use the new methods.
  • Let us first develop an abstract class to facilitate the development of multiple iterations of our component. Abstract classes make it possible to version our components in a straightforward and uncomplicated way. When a change is made to the base class, any inheriting classes that use that class will automatically receive the update. On the other hand, after an interface has been developed, any alterations to it are not possible. If we need a new version of an interface, we will have to develop an entirely new one.
  • Abstract classes have the benefit of allowing for better forward compatibility, which is a significant advantage. Once clients begin using an interface, we cannot make any changes to it; however, if they use an abstract class, we can still add behaviour without breaking the code that has already been put in place.
  • Make use of an abstract class if providing functionality implemented consistently across all of our component’s implementations is your goal. Comparatively, interfaces do not include any implementation for any members, whereas abstract classes give us the ability to implement our class partially.
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What Exactly Is Interface

An interface resembles a class, but it is not a class. An interface, similar to a class, can have methods and variables; however, methods declared within an interface are automatically considered abstract. The absence of a body in interface methods makes them ideal for use in providing complete abstraction.

Therefore, the class needs to implement them first before anyone can attempt to access them. In most cases, a class that implements an interface is required to define all of the methods declared in the interface; if this is not the case, the class must be declared abstract.

If a class doesn’t implement each of the interface’s methods, the interface is considered incomplete. Because Java doesn’t let us make the interface work for more than one class, we must use the interface keyword to declare an interface and the implements keyword to make it work. Both of these keywords are required when working with interfaces.

Reasons For Employing Interface

  • Interfaces are how abstraction can be accomplished.
  • Developed to facilitate the resolution of dynamic method conflicts while the programme is being executed.
  • This will allow you to achieve loose coupling.
  • This feature allows you to decouple method definitions from their parent inheritance structures..

Use Cases For Interface

  • Use an interface if our functionality will be useful for a wide range of objects. While interfaces provide the same functionality to multiple classes, abstract classes are used for closely related objects.
  • We should consider using interfaces when we anticipate that the API will not undergo significant changes shortly.
  • Interfaces are helpful when we want something analogous to multiple inheritances because we can implement multiple interfaces. This makes interfaces a versatile design pattern.
  • Use interfaces if we design short snippets of functionality and to the point. When it comes to the design of large functional units, we ought to always make use of abstract classes.

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Abstract Class vs. Interface Java

In contrast, an interface allows you to declare functionality but not implement it. On the other hand, an abstract class allows you to design functionality that subsequent subclasses can decide whether or not to implement. A particular class can extend only one abstract class; however, that class can implement various interfaces.

              Interface              Java
Implement several Interfaces A single abstract class  
Abstract proceduresProcedures that are both abstract and concrete
Future enhancementTo avoid independence
A Class can use several interfaces.   Only one Abstract Class can be the parent class of this Class.
When adding new elements to the interface, it is a nightmare to locate all implementors and implement the newly defined elements   In the case of Abstract Classes, the default implementation can be utilized.  
The interface is devoid of access modifiers. Everything defined within the interface is presumed to be public.    Access modifiers are permissible in Abstract Classes.
When multiple implementations share only method signatures, it is preferable to employ an interface. Hierarchy of polymorphic value types.    It is useful when several different implementations of the same type behave similarly.    
The interface is incompatible with data fields.    The class may contain fields for data.  
One class can support several interfaces.    One abstract class is the maximum that a class can inherit.
Abstract interfaces are incapable of providing code.  Abstract classes can provide default code that must be overridden.    
Access modifiers cannot be used on the method, its properties, or anything else.You can utilize an abstract class with access modifiers.
Interfaces aid in defining a class’s ancillary skills.A class’s identity is defined by its abstract class.
You cannot define any fields.Abstract classes permit the definition of both fields and constants.
An interface may inherit from other interfaces, while classes cannot.Abstract classes can inherit from both classes and interfaces.
No constructors or destructors can be declared in an interface.An abstract class may declare constructors and destructors.  
It can extend multiple interfaces.It can only extend a single class or abstract class.      
When declaring a method as abstract in an abstract interface, the keyword is optional.The abstract keyword must be used to declare a method as abstract in an abstract class.
Only abstract public methods may be included in an interface.Abstract classes contain both private and public abstract methods.

Final Words

In summary, it gives an overview of abstract vs. Interface. These ideas about Java Interface vs. Abstract Class will help you understand them better.As circumstances dictate, we can employ either Java Interface or Java Abstract Class alone. However, the combination of interfaces and abstract classes is the most effective design method.

We can place the code that a class needs to share in an abstract class when the class needs to share some code. When we need to know the state of an object, we can define a non-final or non-static field and then use an abstract class. An interface is an option for us to consider when we require full abstraction, multiple inheritance, and loose coupling. Join the ProIT Academy institute to learn about abstract and Interface in Java.

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