Ioane5

package models

sealed class Expression
class Literal(val value: Double) : Expression()
class Addition(val left: Expression, val right: Expression) : Expression()

abstract class ExpressionOperator<T> {
    abstract fun operate(literal: Literal): T
    abstract fun operate(addition: Addition): T
    fun operate(expression: Expression): T = when (expression) {

Ioane5

package ge.example.yourPackageName

import android.app.Dialog;
import android.content.Context;
import android.content.DialogInterface;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.StringRes;
import android.support.v4.app.DialogFragment;
import android.support.v7.app.AlertDialog;