class SortedListSampleAdapter : RecyclerView.Adapter<SortedListSampleAdapter.UserViewHolder>() {

    private val userSortedList: SortedList<User>

    init {
        userSortedList = SortedList(User::class.java, object : SortedListAdapterCallback<User>(this) {
            override fun compare(o1: User, o2: User): Int = o1.score - o2.score;

            override fun areContentsTheSame(oldItem: User, newItem: User): Boolean = oldItem.id == newItem.id

            override fun areItemsTheSame(item1: User, item2: User): Boolean = item1 == item2
        })
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): UserViewHolder {
        val view = LayoutInflater.from(parent.context).inflate(R.layout.item_user, parent, false)
        return UserViewHolder(view)
    }

    override fun onBindViewHolder(holder: UserViewHolder, position: Int) {
        holder.setUser(userSortedList.get(position))
    }

    override fun getItemCount() = userSortedList.size()

    fun addUser(user: User) {
        userSortedList.add(user)
    }

    fun addUsers(users: List<User>) {
        userSortedList.addAll(users)
    }

    fun removeUser(index: Int) {
        if (userSortedList.size() == 0) {
            return
        }
        userSortedList.remove(userSortedList.get(index))
    }

    class UserViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {

        var textViewUsername: TextView = itemView.findViewById(R.id.textViewUserName)
        var textViewBirthDate: TextView = itemView.findViewById(R.id.textViewBirthDate)
        var textViewScore: TextView = itemView.findViewById(R.id.textViewScore)

        fun setUser(user: User) {
            textViewUsername.text = user.name
            textViewBirthDate.text = "Age: " + user.age
            textViewScore.text = "Score:" + user.score
        }
    }
}