What can you tell about properties, and get and set methods in Kotlin?

In Kotlin, properties are a combination of a field and its corresponding getter and setter.

Property definition:

class MyClass {
    var mutableProperty: String = "default"
    val immutableProperty: Int = 10
}

Here, mutableProperty is a mutable property with default getter and setter. immutableProperty is an immutable property with only a default getter.

Explicit getter and setter definition:

class MyClass {
    var customProperty: String = ""
        get() = field.toUpperCase() // Custom getter
        set(value) {
            field = value.toLowerCase() // Custom setter
        }

    val computedProperty: Int
        get() = (1..10).random() // Computed property, has no backing field
}

• field is a back-reference to the property backing field inside getter and setter. It is used only for mutable properties (var).
• Getters and setters can be customized to perform additional logic when accessing or modifying the property.
• Computed properties (computedProperty) do not have a backing field and always calculate their value upon access.

Key points:

• In Kotlin, there is no need to explicitly create getters and setters for each field as in Java. They are generated automatically.
• Properties are accessed via dot notation (instance.propertyName).
• Explicit getter and setter definitions allow adding logic during access or modification.
• Getters for val properties must always return a value of the same type.
• Setters for var properties accept a parameter of the same type.

Comparison of properties in Kotlin and fields+methods in Java:

Kotlin Property	Java Field + Methods	Description
var myProperty: Type	private Type myProperty; + public Type getMyProperty() + public void setMyProperty(Type value)	Mutable property with automatic getter and setter.
val myProperty: Type	private Type myProperty; + public Type getMyProperty()	Immutable property with only an automatic getter.
Custom getter/setter	Explicit logic implementation	Adding custom logic during access/modification.
Computed property	Explicit method returning value	Property value is computed upon each request.