Kotlin OOPs Concepts (OOPs in Kotlin With Examples)

Kotlin is a modern, statically-typed programming language that fully supports OOP principles. It allows you to define classes, create objects, and utilize key OOP concepts such as inheritance, encapsulation, and polymorphism.

A primary constructor is defined in the class header, while a secondary constructor is defined using the constructor keyword inside the class body. Primary constructors are used to initialize class properties, while secondary constructors provide additional ways to create class instances.

Inheritance in Kotlin allows a class (subclass or derived class) to inherit properties and methods from another class (superclass or base class). You use the : symbol to indicate inheritance. Subclasses can override methods and properties from the superclass.

A data class in Kotlin is a class that is specifically designed to hold data, such as properties and nothing more. Kotlin automatically generates equals(), hashCode(), toString(), and copy() methods for data classes. You should use data classes when you need to represent simple data structures.

Kotlin supports multiple inheritance through interfaces. A class can implement multiple interfaces, which allows it to inherit and provide implementations for methods declared in those interfaces. This is a way to achieve multiple inheritance without the complexities associated with it in some other languages.

In Kotlin, the open keyword is used to mark classes and methods as open for extension. It allows you to subclass a class or override a method in a subclass. By default, classes and methods in Kotlin are final and cannot be overridden or extended unless marked with open.

Yes, you can define properties with custom getters and setters in Kotlin using the get() and set() keywords. This allows you to add custom logic when getting or setting the property's value.

The internal modifier restricts visibility to within the same module (project or module-level access). It is useful for creating modules with encapsulated implementation details that are not visible outside the module.

A sealed class is a special type of class that restricts the inheritance hierarchy to a predefined set of subclasses. It is often used in conjunction with when expressions to handle a limited set of cases exhaustively.

Abstract classes can have properties and methods with implementations, and they can be subclassed. Interfaces, on the other hand, cannot contain implementation details and are implemented by classes. A class can inherit from only one abstract class but implement multiple interfaces.

You can prevent a class from being subclassed by marking it as final. A final class cannot have subclasses. Additionally, you can achieve this by not marking the class as open, which is the default behavior in Kotlin.

The by keyword is used for delegation in Kotlin. It allows one class to delegate the implementation of some of its methods or properties to another object. Delegation is a way to reuse and compose behavior in a class.

The companion object is a way to define static members (properties and methods) within a class. These members are associated with the class itself rather than instances of the class. It provides a way to create class-level functionality.