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Choosing Between Interface and Abstract Class in Java: A Quick Guide

Those even vaguely familiar with Java know that it includes interface and abstract class. The interface is a template that can be leveraged to implement a class, an abstract class with abstract keyword declaration.

A developer working with Java will have to choose between the two. However, the decision can often prove to be complicated since it involves detailed reasoning. For example, one may suggest opting for interfaces since it supports various inheritances while another might argue in favor of an abstract class since it enables the implementation of a few methods in the parent class.

So, allow us to tell you about interfaces and abstract classes in detail. It will help you make an informed decision between Abstract and Interface Class.

1. Abstract class

Abstract classes aim to encapsulate the general characteristics of subclasses. It is crucial to note that an abstract class can’t be instantiated and can only be utilized as a superclass by its subclasses. Also, bear in mind that they are used to build a template for their subclasses down the hierarchy.

Though abstract classes enable the creation of blueprints for concrete classes, the inheriting class must necessarily implement the abstract method. Interestingly, this is why Java doesn’t support multiple inheritances for abstract classes — since a concrete class can assume the properties of only one abstract class.

When and why you should use an abstract class

a. It provides default functionality for the subclasses

b. Offering a template for future specific classes

c. An abstract class can be used to define a standard interface for its subclasses

d. The creation of an abstract class has nothing to do with the provision or the absence of the implementation of any method

2. Interface

An interface is an amalgamation of abstract methods, and since a class implements an interface, it inherits the interface’s abstract methods. It is basically like signing a contract, wherein the developer agrees that if a particular interface is implemented, they have to use its methods. Whereas an interface is merely a pattern and it can’t do anything itself.

Since a class can have various behaviors, Java allows developers to implement an unlimited number of interfaces. Furthermore, since the aim of an interface is only to provide behaviors, it is advisable to use adjectives while naming the interface.

When and why you should use an interface

a. Interfaces are aimed at supporting dynamic method resolution at runtime

b. An interface is used to attain abstraction

c. It enables you to disunite the definition of a method from the inheritance hierarchy

d. Interfaces also facilitate loose coupling

As we mentioned earlier, the decision to use an interface or an abstract class can be a tad complex. So, use this handy guide to decide which one will serve your needs better. Moreover, no matter how big or small your project may be, it’s a good idea to engage the services of a certified Java programmer, from a reputed software development company to make sure that the end product lives up to every bit of your expectations and fulfills all your requirements.

Written By

A professional and security-oriented programmer having more than 6 years of experience in designing, implementing, testing and supporting mobile apps developed. Being techno geek, I love to read & share about the latest updates in technology including but not limited to IoTs, AI, application development, etc. In my free time, I like to play football, watch movies and explore new places. I have been learning mobile app development since 2012. With having a good understanding of programming languages, I develop native as well as web apps for both iOS & Android using latest tools & technologies. I am also having experience in both front-end & back-end development.

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