``` val number:Int = 127 val boxedNumber: Int? = number val anotherBoxedNumber: Int? = nu...

# getting-started

[Gamar Mustafa]

val number:Int = 127
    val boxedNumber: Int? = number
    val anotherBoxedNumber: Int? = number
    println(boxedNumber === anotherBoxedNumber) // true

Why does this case exist? And why it only works for byte ranged numbers?

[Joffrey]

On the JVM, boxed instances of Integer are cached for low int values

[Riccardo Lippolis]

see for more info: https://medium.com/geekculture/integercache-in-kotlin-java-c2044b12de2c

[Gamar Mustafa]

@Joffrey it's true for Long too:

val number:Long = 127
val boxedNumber: Long? = number
val anotherBoxedNumber: Long? = number
println(boxedNumber === anotherBoxedNumber) // true

[Gamar Mustafa]

@Riccardo Lippolis thanks for the link! reading right now

[Riccardo Lippolis]

there are cached values for boxed versions of multiple primitive data types, so e.g. Integer, Long, Short, Byte, Character, Boolean

[Joffrey]

The specification defines this cache in section "5.1.7. Boxing Conversion" here:
https://docs.oracle.com/javase/specs/jls/se22/html/jls-5.html#jls-5.1.7

So it talks about "integer values" in general, but this should cover byte/short/int/long. Note that this caching is defined as a minimum, but different implementations of the JVM may choose to cache more

[Riccardo Lippolis]

ah yeah, Short, forgot that one 😅

[Joffrey]

Overall, you shouldn't make assumptions about the identity of these types, boxed or not. This is why Kotlin forbids === for primitives, by the way. Use == instead to check for equality (not identity)

[Gamar Mustafa]

Thanks a lot! @Joffrey @Riccardo Lippolis. I got it now)