DEV Community

loading...

Kotlin Equality – Difference between “===” vs “==”

loizenai profile image loizenai ・1 min read

https://grokonez.com/kotlin/kotlin-equality-difference-referential-equality-vs-structural-equality

Kotlin Equality – Difference between “===” vs “==”

In the tutorial, Grokonez will introduce Kotlin Equality, the difference between === and ==.

I. Kotlin Equality

We have 2 types of Kotlin equality:

  • Referential equality with === operation
  • Structural equality with == operation

    1. Referential equality

    Referential equality is used to check references with same pointing object. It represents with === operation (negative form !==).

// ###########################
// 1. referential equality
// ###########################
val str = "a"
val str1 = "a"
println(str===str1)
/*
    true
    -> a & b point to the same object
*/

val i = Integer(10)
val j = Integer(10)
println(i===j)
/*
    false
    -> i & j point to the difference objects
*/

val jack = Customer("Jack", 25)
var customer = jack;
println(jack === customer)
/*
    true
    -> Because 'jack' and 'customer' objects point to the same object 
*/  

customer = Customer("Jack", 25)
println(jack === customer)
/*
    false
    -> Because 'jack' and 'customer' objects point to the difference object 
*/

2. Structural equality

Structural equality is used to check equality of objects by equals() function with == operation (negative form !=)

a==b is translated to a?equals(b) ?: (b === null)

More at:

https://grokonez.com/kotlin/kotlin-equality-difference-referential-equality-vs-structural-equality

Kotlin Equality – Difference between “===” vs “==”

Discussion (0)

Forem Open with the Forem app