Questions tagged [kotlin]
Kotlin is a statically typed programming language that compiles to JVM bytecode, JavaScript, or native binaries.
258
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Small DSL for SQLite's where clause
I've got an application with a filter that offers the user over 30 different search cirteria that I need to translate into an SQLite query. A small DSL should simplify creating more efficient ...
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Android: Navigation with Hilt + Jetpack Compose
The project is simple:
Login screen and a forgot password screen. You can navigate from Login to ForgotPassword.
I feel like I overcomplicated things, but I don't know if (and how) it can be ...
CommunityBot
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Solve the snake cube puzzle
I wrote a solver for the snake cube puzzle. The solver can be easily adapted to arbitrary snakes.
Since the program takes only a few seconds to run, I didn't care to optimize for speed, instead I ...
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Constructing constrained/validated objects
I'm trying to do some rudimentary DDD in validating my objects to ensure they are of a particular type. I.e. an Email object would always look like "[email protected]" ...
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Wrap location API in coroutines
In my app I need to query location and scan wifi periodically. To conserve power I need to change the rate dynamically, depending on the distance to the target. Also I want to wait for both ...
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Getting a value with timeout using Kotlin coroutines
So, here's a task. A background thread may or may not call all of it's listeners some time after sendRequest() was called (in other words ...
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Am I wrapping synchronous code in ktor/Kotlin coroutine correctly?
I'm playing with ktor right now. If I understand this correctly, code in ktor's handlers need to be as asynchronous as possible. So I was trying to figure out how do you write synchronous (potentially ...
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Correct flow between Kotlin, Realm and ViewModels using Coroutines
I'm stepping back into Android after being away from it for about a year. Trying to get an out of date app of mine back on its feet, and continuing work on it.
The app was written using Java, MVP, ...
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Lock-free implementation of getAndUpdate() using atomic CAS (Compare-And-Swap) operation
We have the following class written in Kotlin Native with the new Memory Manager (which doesn't require to freeze objects):
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CommunityBot
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Chess in Kotlin
This is an updated version of my first question:
Chess game in Kotlin
I wrote the following Chess logic in Kotlin and am looking for feedback to make the code cleaner and follow good software design ...
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Mapping named parameters to indices for PreparedStatement
I needed something to map named SQL parameters into indices for JDBC queries so I wrote the ParameterMap class that takes an SQL query, searchers for parameters ...
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Mapping named parameters to indices for PreparedStatement as DSL - follow-up
In the previous question I showed you my first attempt to handle named SQL parameters with JDBC and you were right, it wasn't as intuitive as I thought. The ...
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Import large Excel files directly from XML streams into an SQLite database
I've got some pretty large Excel files with nearly 1M rows that are almost impossible to open and work with in Excel anymore that I'm migrating into a database. Desipte this these files will stick ...
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TicTacToe OOP approach in Kotlin
I wrote a terminal-based TicTacToe game in Kotlin to practice both Kotlin and OOP. Any feedback on structure and code would be appreciated.
Board.kt
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Kotlin function which counts standard deviation
Here is the code. The code should counts the standard deviation for double array, but also for Int arrays.
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Kotlin call API and store JSON files locally
I'm new to Kotlin and wanted to give this mini project a try. Please let me know if you have any improvements in mind. I'm thinking error handling, structuring the module, is there too much going on ...
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Swift-function which counts the letters, numbers, spaces, special chars in a given string
Task description: Write a function, which counts the letters, spaces, number and special characters in string.
My implementation:
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Jetpack Compose: Length-Units Converter
I have made a length-units converter with Jetpack Compose.
Here's the source-code:
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Architecting my Compose UI
I have designed a layout that includes recipe details and three CTAs in the app bar to share, delete, and edit recipes. I need feedback regarding the architecture of my Compose UI.
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Simple Kotlin Bingo Class
This is a simple class in Kotlin that handles three basic Bingo-related functionalities: Specifying the numbers, generating a card, and calling one random element. Additionally, it should support an ...
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Loading-content-error implementation for a tiny Kotlin library
I have a sealed interface that I use in pretty much every one of my Android projects. It implements the loading-content-error pattern, often called a Resource, <...
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Assert MockMvc response by using Kotlin DSL
I build web application using Kotlin and Spring Boot, I use MockMvc to write integration test.
I'm not satisfied how assertion looks like, here is typical assertion:
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Word-guessing game
The objective of the game is to guess a five-lettered word in five guesses or less. When the user (player) enters a word, the application will inform the user whether their guess was correct or not. ...
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Given an EAN-8 or an EAN-13 code, tell if that code is valid
I have the requirement to validate product codes which include EAN-8, EAN-13 and UPC-A encoded as EAN-13. I have implemented a use-case to perform this check by comparing the actual check digit with ...
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Remove inputted keys separated by spaces from map and output the resulting map, including alias recognition
I'm looking to integrate Kotlin idioms (including code style) and maybe better performance. I wonder if there's a better way to do line 17 (the str.split(' ') one).
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Learning Jetpack Compose: TabBar with Paging Screens
I'm piecewise reimplementing an existing iOS app. My initial go at it visually looks like this:
I'm looking for any feedback on more idiomatic ways to implement what I've done. There's a couple of ...
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Generate unique string permutations recursively
🧩 Objective
Write a recursive method for generating all permutations of an input string. Return them as a set.
See: Recursive String Permutations - Interview Cake
🔎 Questions
1: How does the ...
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Advent of Code 2021 Day 19
I am taking advantage of the recent layoffs to teach myself Kotlin. I am a career Java programmer, I've touched Kotlin before but not actively, and not for a few years. I wrote it all in one file ...
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Jetpack Compose: Items-list with Item-Details-view
The app is based upon an exercise from a Udemy-course. The purpose is to become familiar with LazyColumns. I've enhanced the exercise with a Details-view and a navigation between LazyColumn and ...
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Kotlin JSR 310 validation annotation
So, I am trying to implement an annotation in Kotlin, and it works, but I definitely feel like I could do a lot better. Below is the code and some areas I think could be improved. The purpose of this ...
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An automated jOOQ-query-builder based on input using JSON in Kotlin
In my current project, I have to build a criteria builder which users can use to find "contacts" (the definition of which is not relevant). For this, I have created the front-end in Elm, ...
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Removing repeating rows and columns from 2d array
This is a real problem I had to fix recently. Imagine having generic array where you can have duplicate columns and rows.
You want to remove those duplicates as long as they are next to each other.
<...
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Splitting a list in Kotlin
I want to split a list (as if splitting a string by a delimiter), ideally in a functional style, and was surprised how hard it seems to be. Or maybe my code is just unnecessarily complicated?
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Temperature Scale Converter in Kotlin
Problem statement:
Write a program that converts all given temperatures from a given input temperature scale to a given output temperature scale. The temperature scales to be supported are Kelvin, ...
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Function to capture all stdout to String
I wanted to have a simple way to capture all sysout for a block of code. Ended up with this:
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MutableLiveList class for android
I have wrote a MutableLiveList class for android, similar to existing MutableLiveData, but this class instead handles a list and ...
CommunityBot
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Android - A way to show/hide loader without writting false/true in every viewmodelScope.launch
I have been writting a lot of code that looks like this
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Android + Kotlin advanced color picker (HSV and RGB)
For almost the past year, I have been working on a pixel art editor for Android.
My pixel art editor was relying on an external library for its color picker. For 0.2.0, I wanted to change this by ...
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Observe LiveData to indicate whether or not to display TextViews in MVVM
In the context of MVVM, is this an efficient way to communicate to the view that I should display some TextViews? Any advice on how I can improve it?
ViewModel code:
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Processing charge current error messages with HashMap<>
I have certain error states that I am displaying in my Android TextView but only one message is displayed at a time and if all values are set to 0, no message is displayed. So, I check all the values ...
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Load data from database, change it asynchronously and return the new data
I have written this function to load data from the database, change it asynchronously and return the new data. It appears to work fine, but since I am new to Kotlin, I wanted to ask if this code is ok ...
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parsing source code to generate documentation of an open source program (StreetComplete, an OpenStreetMap editor) - 1180 lines of Kotlin script
All help welcomed!
I posted a big chunk of code here - but feel free to review only a small section. I will use answers to improve this deployed open source software.
About the code
This code works. ...
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912
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Jetpack compose login screen + ViewModel
Im working on the login screen for my application. It has fields for users email and password. Also users can click on forgot password button to send an email with new passsword. It can validate these ...
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Performing complex operation before calling the primary constructor in Kotlin
Semester is a simple enum class.
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Produce an arithmetic progression
I have made a function which takes in an end point and a step, then produces a list of integers with the step in mind. For example, if the end point is 10 and the step is 2, the function should return ...
Mast♦
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Android architecture and dependency injection of domain layer usecases
I am implementing some of the architectural designs from Google I/O's app to my own app, but I have come across something in their app that has created some confusion for me.
They have a domain layer ...
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Adapter pattern apply with JsonObject
The purpose of the code is to apply adapter pattern to put an extra feature for searching through json object.
I hate deep nested json object because it makes my code look messy when access through ...
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Iterative Fibonacci number generator in Kotlin
I have very limited experience in Java and slightly more in C# (just doing Advent of Code problems last month), so I'm not familiar with how to write idiomatic Kotlin.
This class implements an ...
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Aggregate data from a huge list under 50ms
I got this question as a coding challenge and was unable to get it done under 50 milliseconds (my solution takes >100 ms) :D
Would you please review my code and share any idea how to do this within ...
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