use static Java methods as static (or singleton) properties in Kotlin

Question

My SDK exposes a Java interface that has only static methods, e.g.

public interface MyDevice { 
  public static void setLocation(Location location) {…}
  public static Location getLocation() {…}
}

In Java app that uses the SDK, my customers can use these as if it were a singleton, e.g.

Location currentLocation = MyDevice.getLocation();

When this SDK is integrated into a Kotlin app, it would be natural to express the same as a property:

val currentLocation = MyDevice.location

The problem is, this built-in interop works for non-static methods only.

I can create a singleton in Kotlin and have it handle the translation:

object myDevice {
    var location: Location
    get() = MyDevice.getLocation()
    set(location) = MyDevice.setLocation(location)
}

But won't this single Kotlin file in an otherwise Java-only SDK negatively affect the customers who don't use Kotlin? Can the same be expressed in Java?

Or maybe I should simply convert MyDevice.java to Kotlin? What will be negative effects of such step for the customers who are still on Java?

Answer 1

The problem you described is a lack of meta data Kotlin need to treat static methods as Class extension properties of extension functions.

Together with issue KT-11968 it makes it not possible for now, at least.

The best possible option is API conversion to Kotlin with a support of @JvmStaic/@JvmField and @JvmDefault where necessary for backward compatibility.

interface MyDevice {
  companion object {
    // nullable type or explicit init
    var location: Location? 
      @JvmStatic get
      @JvmStatic set


// kotlin
val x = MyDevice.location
MyDevice.location = x


// java
var x = MyDevice.getLocation();
MyDevice.setLocation(x);