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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.
|Instantiation||Cannot be instantiated||Cannot be instantiated|
|Inheritance||Can be extended using the ‘extends’ keyword||Can be implemented using the ‘implements’ keyword|
|Access Modifiers||Can have any access modifier||All methods are public by default|
|Variables||Can have instance variables||Cannot have instance variables|
|Constructors||Can have constructors||Cannot have constructors|
|Methods||Can have both abstract and non-abstract methods||Can only have abstract methods|
|Implementation||Subclasses must implement abstract methods||Classes that implement an interface must provide an implementation for all of its methods|
|Multiple Inheritance||Cannot extend multiple classes||Can implement multiple interfaces|
|Compatibility||Can change existing concrete methods||Cannot change the existing methods of a class|
|Flexibility||Provides more flexibility in designing class hierarchies||Provides more flexibility in allowing unrelated classes to implement a common set of methods|
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.
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