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In Kotlin, visibility modifiers control where classes, properties, functions, and constructors can be accessed from. The main visibility modifiers are: public private protected internal If you do not specify a visibility modifier, Kotlin uses public by default. 1. public public means the declaration can be accessed from anywhere. class User { public val name: String […]
In Kotlin, interfaces define a contract that classes can implement. Kotlin supports multiple inheritance of interfaces, but not multiple inheritance of classes. 1. Defining an interface An interface can declare: abstract properties abstract functions functions with default implementations interface Drivable { val maxSpeed: Int fun drive() fun stop() { println("Stopping the vehicle") } } Here: […]
In Kotlin, classes and members are final by default, so you must explicitly mark them as open if you want them to be inherited or overridden. Basic class inheritance open class Animal { open fun makeSound() { println("Some sound") } } class Dog : Animal() { override fun makeSound() { println("Bark") } } Usage: fun […]
In Kotlin, an init block runs setup logic when a class instance is created. It is commonly used to validate constructor arguments, initialize derived properties, or perform other construction-time setup. class User(val name: String, val age: Int) { init { require(name.isNotBlank()) { "Name must not be blank" } require(age >= 0) { "Age must be […]
In Kotlin, you usually don’t manually override toString(), equals(), and hashCode() if your class is just a value/data holder. Use a data class instead. data class User( val id: Int, val name: String ) Kotlin automatically generates: toString() equals() hashCode() copy() componentN() Example: val a = User(1, "Alice") val b = User(1, "Alice") println(a) // […]
In Kotlin, data classes are designed to store structured data with minimal boilerplate. A data class automatically provides useful functions such as: toString() equals() hashCode() copy() component functions for destructuring, like component1(), component2() Basic example data class User( val id: Int, val name: String, val email: String ) You can create and use it like […]
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