📌 Constructors in Kotlin

In Kotlin, a constructor is a special function used to initialize objects. It is called when an object of a class is created.

Kotlin supports two types of constructors:

1. Primary Constructor

2. Secondary Constructor

✅ 1. Primary Constructor

• The primary constructor is part of the class header.

• It is used to initialize class properties directly.

• The keyword constructor is optional if there are no annotations or visibility modifiers.

📌 Syntax:

kotlin
class ClassName(val property1: Type, var property2: Type) {    // Class body}

📌 Example: Primary Constructor

kotlin
class Person(val name: String, var age: Int) {    fun () {        println("Name: $name, Age: fun () {    val person = Person("John", 25)    person.displayInfo()}

Output:

yaml
Name: John, Age: 25

• val name → Immutable property.

• var age → Mutable property.

📌 Primary Constructor with Initialization Block (init)

• The init block is executed when the object is created.

• It is useful for additional initialization or validation.

kotlin
class Employee(val name: String, var salary: Double) {    init {        println("Employee $name created with salary fun main() {    val emp = Employee("Alice", 5000.0)}

Output:

csharp
Employee Alice created with salary 5000.0

✅ 2. Secondary Constructor

• Secondary constructors are defined using the constructor keyword inside the class body.

• They can include additional logic or initialization.

• If the class has a primary constructor, the secondary constructor must call it using this().

📌 Example: Secondary Constructor

kotlin
fun () {        println("Name: $name, Grade: fun () {    val student1 = Student("Mark", "A")    student1.displayInfo()    val student2 = Student("Sophia")    student2.displayInfo()}

Output:

yaml
Name: Mark, Grade: AGrade not provided, setting default grade.Name: Sophia, Grade: Not Assigned

✅ 3. Constructor with Default Values

Kotlin allows you to define default values for constructor parameters to make object creation more flexible.

📌 Example: Constructor with Default Values

kotlin
class Car(val brand: String = "Toyota", val model: String = "Corolla", val year: Int = 2024) {    fun () {        println("Brand: $brand, Model: fun main() {    val car1 = Car()    car1.displayInfo()    val car2 = Car("Honda", "Civic", 2023)    car2.displayInfo()}

Output:

yaml
Brand: Toyota, Model: Corolla, Year: 2024Brand: Honda, Model: Civic, Year: 2023

✅ Conclusion

• Use Primary Constructor for simple object initialization.

• Use Secondary Constructor when additional initialization logic is needed.

• Use init Block for executing code during object creation.

• Provide Default Values for constructor parameters to simplify object creation.