How to get name from Java enum in Kotlin

Question

I have a project that is written with both Java and Kotlin languages and recently I faced next issue.

Let's say we have MyMonth enum:

public enum MyMonth {
    JAN("January"),
    FEB("February");

    private final String name;

    MyMonth(final String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }
}

Then in Kotlin when we print the name of the month:

fun main() {
    val month = MyMonth.JAN
    println(month.name)
}

we get:

JAN

which is what is described in the documentation https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-enum/name.html, however actually the name should be January.

Is there a way to get a name in Kotlin that is specified in Java enum?

UPD: My Kotlin version is 1.3.30-release-170

UPD2: IDEA even shows me that name is coming from the getName() method defined in Java:

UPD3: When we explicitly use .getName() it works, however it looks kind of weird

My guess is since Kotlin enums already have a name property, as seen here, there's a conflict between the Java getter and the Kotlin property. If possible, I recommend changing the name of the Java field and getter to something other than name and getName(). Personally, I think it's a bad idea to have a field named name in a Java enum anyway, considering the existence of the name() method. If you can't change it, what if you call getName() explicitly in the Kotlin code? — Slaw
– Slaw, Commented Nov 26, 2019 at 18:02

Minn · Accepted Answer · 2019-11-26 18:04:26Z

5

You can call the getter directly instead of using the property syntax:

fun main() {
    val name = MyMonth.JAN.getName()
    println(name)
}

answered Nov 26, 2019 at 18:04

Minn

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3 Comments

Nikolai Shevchenko Over a year ago

@Orest that's because name is reserved in enums. If you could pick another property name, then it would be non-excessive

Minn Over a year ago

@Orest you could make an extension property which calls getName() to make it look more idiomatic

Orest Over a year ago

@NikolaiShevchenko yes, it's clear to me, however I already mentioned that in the comments that it's not that rare when you have to use an enum that comes from Java with name field and you're not able to change it

Louis Wasserman · Accepted Answer · 2019-11-26 17:43:21Z

3

Your Java API has name as a private field. Nothing can access it, not in Java nor Kotlin.

If you want to access it, add e.g. the following to the Java API:

public String getMonthName() { return name; }

...and then access it from Kotlin as

val month = MyMonth.JAN.monthName

answered Nov 26, 2019 at 17:43

Louis Wasserman

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4 Comments

Orest Over a year ago

In Java I can simply add a getter and call MyMonth.JAN.getName() which would return me what I need. But this getter is not used in Kotlin even though IDEA show me that it's from there, I'll update my question to make it more clear.

Orest Over a year ago

Hey @Slaw that's a good suggestion, unfortunately it's not possible to rename that field as I'm not the owner of the library that has this enum. Also, I think it's not that rare when you have a Java enum that has field name in it.

Louis Wasserman Over a year ago

name is specifically complicated by being already baked into the definition for enums. You may just have to call getName() explicitly and not use it as a property, even if IntelliJ tells you you don't have to. It may be outright lying.

Orest Over a year ago

Yes I understand that name is baked into Kotlin enum, just noticed this weird behavior and was confused for a while. Thanks!

Prabudda Fernando · Accepted Answer · 2019-11-27 05:38:47Z

0

enum is now low usage. You can use IntDef instead of enums.

@IntDef(MyMonth.JAN, MyMonth.FEB)
@Retention(AnnotationRetention.SOURCE)
annotation class MyMonth  {
    companion object {
        const val JAN = 0
        const val FEB = 1

        fun getDisplayString(toDoFilterTypes: Int): String {
            return when (toDoFilterTypes) {
                JAN -> "All"
                FEB -> "Job"
                else -> "N/A"
            }
        }
    }
}

answered Nov 27, 2019 at 5:38

Prabudda Fernando

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1 Comment

Ricky Clarkson Over a year ago

This seems to be outdated now - medium.com/default-to-open/…

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