Java Abstract Class vs Interface

When it comes to Java programming, both abstract classes and interfaces are used to achieve abstraction. While they have some similarities, they differ in their implementation and usage. In this tutorial, we will compare the main differences between abstract classes and interfaces in Java, in the form of a comparison table.

FeatureAbstract ClassInterface
InstantiationCannot be instantiatedCannot be instantiated
InheritanceCan be extended using the ‘extends’ keywordCan be implemented using the ‘implements’ keyword
Access ModifiersCan have any access modifierAll methods are public by default
VariablesCan have instance variablesCannot have instance variables
ConstructorsCan have constructorsCannot have constructors
MethodsCan have both abstract and non-abstract methodsCan only have abstract methods
ImplementationSubclasses must implement abstract methodsClasses that implement an interface must provide an implementation for all of its methods
Multiple InheritanceCannot extend multiple classesCan implement multiple interfaces
CompatibilityCan change existing concrete methodsCannot change the existing methods of a class
FlexibilityProvides more flexibility in designing class hierarchiesProvides more flexibility in allowing unrelated classes to implement a common set of methods
Abstract Class vs Interface

The above comparison table outlines some of the key differences between abstract classes and interfaces in Java. It is important to choose the appropriate mechanism for abstraction based on your requirements, as they serve different purposes. Abstract classes are used when you want to provide a common implementation for a set of classes, while interfaces are used to define a contract that classes must adhere to.

Also, see the example code JavaExamples_NoteArena in our GitHub repository. See complete examples in our GitHub repositories.

Follow us on social media
Follow Author