JuniorTheoryCommon

What does the program print (lines separated by spaces)?

KOTLIN

class A(val x: Int)
data class B(val x: Int)

fun main() {
    println(A(1) == A(1))
    println(B(1) == B(1))
}

false true

Expecting true true: thinking == compares the properties of any class. Without its own equals, a plain class answers true only for the same object.
Expecting false false: thinking == always looks for one object. A data class generates equals, so == compares its properties and B(1) == B(1) is true.

JuniorTheoryCommon

KOTLIN

class A(val x: Int)
data class B(val x: Int)

fun main() {
    println(A(1) == A(1))
    println(B(1) == B(1))
}

false true

Expecting true true: thinking == compares the properties of any class. Without its own equals, a plain class answers true only for the same object.
Expecting false false: thinking == always looks for one object. A data class generates equals, so == compares its properties and B(1) == B(1) is true.