Hi guys, Today I noticed weird problem on equals(...

# announcements

[Gokhan Alıcı]

Hi guys,

Today I noticed weird problem on equals() function

it basically;

class Event(val endTime: Long?){
fun isGoingEvent() = ((endTime == null) || endTime?.equals(0))
}

Event(0L).isGoingEvent() ----> returns false

if I change isGoingEvent() implementation with:
fun isGoingEvent() = ((endTime == null) || endTime?.equals(0L))

it works as expected. It make sense because it compares Long with Long
but I confused how should I compare values?

[marstran]

Use endTime == 0. It will give you a compile error if the types don't match. You usually don't use equals directly in Kotlin.

[ribesg]

endTime.let { it == null || it == 0 }

[ribesg]

Wait endTime isn’t a var so this should work

endTime == null || endTime == 0

[Gokhan Alıcı]

but endTime Long so we can't compare like == 0(compile error) my confusion is on equals side which is accepts any type (endTime?.equals(0)) , I would expect it should check type because both of them Number and it should cast correct type and call equals function

[Gokhan Alıcı]

Sample implementation

public open operator fun equals(other: Any?): Boolean

if (other is Number) {
this.equals(other.toLong())
}

[marstran]

Yes, when you are comparing with a Long, you have to do endTime == 0L. Kotlin does not perform any conversions like Java do.

[marstran]

The equals function takes an Any as parameter, so it just doesn't check types at all.

[marstran]

Integer.valueOf(someInt).equals(someLong) will always return false in Java. It's better to have it give a compile error.

[ribesg]

Yes, endTime == 0 would always be false so why allow it anyway? You need

endTime == null || endTime == 0L