Solution: A mutability problem
Any operation that changes the name property will make the code print false. This is because mutableSetOf uses hashCode and equals to check if an element is already in the set. When we add an element to the set, the set calculates its hash code and stores it. When we call contains, the set calculates the hash code of the element we pass as an argument and compares it with the hash code of the element stored in the set. Since the hash code of name is calculated based on the value of the name property, changing the value of this property will change the hash code. Thus, the set will not be able to find the element we are looking for.
fun main() {
val set = mutableSetOf<Name>()
val name = Name("AAA")
set.add(name)
name.name = "BBB" // or any other text
println(set.contains(name)) // false
println(set.first() == name) // true
}
Example solution in playground
fun main() {
val set = mutableSetOf<Name>()
val name = Name("AAA")
set.add(name)
name.name = "BBB" // or any other text
println(set.contains(name)) // false
println(set.first() == name) // true
}
data class Name(var name: String)
