object单例

public class MusicPlayerJava {
    public static MusicPlayerJava INSTANCE = new MusicPlayerJava();
    private MusicPlayerJava(){}
}

class Driver
interface OnExternalDriverMountListener{
    fun onMount(driver: Driver)
    fun onUnmount(driver: Driver)
}
abstract class Player
object MusicPlayer: Player(), OnExternalDriverMountListener{
    override fun onMount(driver: Driver) {
    }
    override fun onUnmount(driver: Driver) {
    }
    val state : Int = 0
    fun play(url : String){
    }
    fun stop(){
    }
}