What is the difference between an abstract class and an interface in Java?

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Ravi Vishwakarma · Answer

Abstract Class An abstract class is a class that cannot be instantiated on its own and may contain abstract methods (methods without a body) and non-abstract methods (methods with a body). Usage: Used when you want to provide a common base class for other classes to extend, while also providing some shared implementation. Example Interface An interface is a reference type in Java that is used to specify a set of abstract methods that a class must implement. From Java 8 onwards, interfaces can also contain default and static methods with implementations. Usage: Used to define a contract that other classes must follow. Interfaces are typically used to represent capabilities or behaviors that can be shared across different classes. Example Key Differences Feature Abstract Class Interface Methods Can have both abstract and concrete methods Can have abstract methods, default methods, and static methods Fields Can have instance variables Can only have public static final fields (constants) Inheritance Supports single inheritance Supports multiple inheritance Constructors Can have constructors Cannot have constructors When to Use Use when classes share a common base class Use to define a contract that multiple classes can implement Read more When to use Interface? What's the difference between an Abstract Class and an Interface in Java? What is the purpose of an interface in OOP?

Feature	Abstract Class	Interface
Methods	Can have both abstract and concrete methods	Can have abstract methods, default methods, and static methods
Fields	Can have instance variables	Can only have public static final fields (constants)
Inheritance	Supports single inheritance	Supports multiple inheritance
Constructors	Can have constructors	Cannot have constructors
When to Use	Use when classes share a common base class	Use to define a contract that multiple classes can implement

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What is the difference between an abstract class and an interface in Java?

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Abstract Class

Interface

Key Differences