Classes
Kotlin Abstract Classes
Abstract Classes
Kotlin abstract classes provide blueprints with abstract members.
What are Abstract Classes?
Abstract classes in Kotlin are classes that cannot be instantiated directly. They are designed to be extended by other classes and can include both abstract methods (without a body) and concrete methods (with a body).
Abstract classes serve as a blueprint for other classes, enforcing a contract for subclasses to implement specific behavior.
Defining an Abstract Class
To define an abstract class in Kotlin, use the abstract keyword. An abstract class can contain both abstract and non-abstract methods. Here's the syntax:
Implementing Abstract Members
When a class inherits from an abstract class, it must provide implementations for all the abstract methods declared within it. Here's how you can implement the abstract class Animal:
Abstract vs. Interface
While both abstract classes and interfaces are used to define methods that must be implemented, they have key differences:
- Abstract Classes: Can have constructors, can hold state, and can contain some implemented methods.
- Interfaces: Cannot have constructors and cannot hold state, but can have default implementations.
Choose abstract classes when you need to provide default behavior or state management.
Key Points to Remember
- Abstract classes cannot be instantiated directly.
- They can contain both abstract and concrete methods.
- Subclasses must implement all abstract methods.
- Abstract classes can have constructors and state.
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