CODEWITHSUNDEEP
classkotlin
Dossanov
Dossanov

Reputation: 131

what's the difference between these classes in Kotlin?

I'm a beginner in Kotlin! Can we explain the difference between these classes in Kotlin

class Person(val name: String, val age: Int)

class Person(name: String, age: Int)

class Person(var name: String,var age: Int)

And how I add getter and setter for data class in Kotlin?

Upvotes: 2

Views: 74

Answers (1)

Simulant
Simulant

Reputation: 20102

First you should try to read the difference in the manual:

https://kotlinlang.org/docs/reference/data-classes.html

https://kotlinlang.org/docs/reference/classes.html

But lets try to explain this:

class Person(val name: String, val age: Int)

The Kotlin compiler will generate for both constructor arguments corresponding fields storing the values and will generate respecting getters. The values are immutable because of the keyword val so there will not be any setters.

class Person(name: String, age: Int)

The arguments are only passed to the constructor but not stored as fields. So there will also be no getters and setters.

class Person(var name: String, var age: Int)

Like in the first example the values are stored in generated fields. But the values are mutable because of the keyword var so the compiler will generate getters and setters.

data is an additional (optional) keyword to put in front of the class declaration. This will in addition to the getters and setters generate a toString method printing the values of all attributes with their names and a hashCode method taking every value into account. As getters and setters are generated for data classes you don't need to add them manually.

Kotlin is a lot about reducing the manual work required to do by the developer in Java to be done by the compiler of Kotlin.

Upvotes: 6

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