Author: Karsten Silz
Feb 21, 2021   |  updated Mar 8, 2021 11 min read


LJC Community Talk: "How Should Java Developers Build Front-Ends for Web, Mobile & Desktop Today?"

LJC Community Talk announcement poster

Table Of Contents


The London Java Community (LJC) regularly hosts community talks. There, two speakers each have 30 minutes for their talks. On Thursday, February 25, 2021, I will present “How Should Java Developers Build Front-Ends for Web, Mobile & Desktop Today?”. I will look at various frameworks from the perspective of a Java developer and suggest which toolkits to use in typical scenarios. Please see the abstract below.

I want to thank Dominique Carlo and Barry Cranford from RecWorks. They make these community talks possible! So if you need to hire Java developers in the U.K., please consider RecWorks!


Users access applications on PCs and mobile devices today. There are two obvious ways to build front-ends for these devices: Web applications and native applications. Cross-platform UI toolkits combine advantages from both approaches. Examples are Facebook’s React Native, Google’s Flutter, Microsoft’s Xamarin, and JavaFX. Important web application frameworks are Facebook’s React, Google’s Angular, and Vue.js. I will look at all these frameworks from the perspective of a Java developer and suggest which one to use in three common scenarios.

In 2019, I developed a mobile app prototype with Flutter and a progressive web application prototype. The videos are below. I then decided to use Flutter for native mobile apps in my current project. Based on my experiences, I will highlight typical Flutter issues and how to solve them.

Why Should You Listen To Me?

I’ve been a Java developer for 22 years. As a full-stack developer, I put three projects into production since 2017. And the fourth one goes live this summer. I was the sole developer on three of them and the lead developer on the fourth one.

I’m not affiliated with the projects I’m discussing here. I’m not selling books or training courses. I’m just sharing industry analysis and my project experiences to give you options for your next project. You then need to apply your own criteria, evaluate these options in your own environment, and make your own choices.


Here are the slides as PDF. They are 3 MB:

You can also get the slides in their original Keynote format. “Keynote” is Apple’s presentation application. Why would you do that? I animated the slides to better convey information and to make them more pleasant to watch. Or maybe you want to peek under the hood to see how I achieved specific effects. These slides include a video and are 14 MB in size!



The talk is on YouTube. It’s 41 minutes long, followed by nearly ten minutes of questions.

Mobile App Prototype with Flutter

In the summer of 2019, I built native iOS/Android apps with Flutter to validate a business problem. It took me about six weeks, and it was my first Flutter project. I used Google’s cloud service Firebase for login, No-SQL database, and file storage. I also built my own back-end with Java, JHipster, Spring Boot, and Angular. This video has the details.

Progressive Web Application Prototype

At the end of 2019, I built a progressive web app (PWA) to speed up app development. A PWA uses the “Service Worker” in a browser to install on your device and cache data. That was about four weeks, and it was my first PWA. I used Google Workbox for this, but developed my own offline storage solution in the browser. I built my back-end with Java, JHipster, Spring Boot, and Angular. This video has the details.

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Looking For Project in October 2021!

And now for some shameless self-promotion: I’m looking to join a project in October 2021, in Milton Keynes, London, or remote. I’ll work as a contractor or fixed-term employee, but don’t take permanent positions. Interested? Then check out my resume & work samples!

Additional Talk Information

Declarative Front-Ends
Apple’s SwiftUI

SwiftUI is Apple’s take on declarative front-ends.

Here’s the counter example from the talk, with slightly changed formatting:

@State var count: Int = 0
var body: some 
View {
  VStack(alignment: .center,
    content: {
      Text("Counter: \(count)").padding()
        action: { self.count++ }, 
        label: { Text("Increment") }
Google’s Flutter

Flutter is Google’s cross-platform implementation of declarative front-ends. It reached the stable version 1.0 for mobile in December 2018.

Here’s what the SwiftUI counter sample looks like in Flutter:

int _counter = 0;

return Column(
  children: [
    Text( 'Counter: $_counter' ),
      onPressed: () => 
        child: Text( 'Increment' ),
Google’s Jetpack Compose

Jetpack Compose is Google’s Android declarative front-ends for implementation of declarative front-ends. Of course, Google has at least two different horses in this race. It’s Google!

Jetpack Compose entered beta on February 24, 20201. According to Google, it now has stable APIs and is feature-complete.

I adopted the counter sample in this tutorial to look like the SwiftUI sample above:

val count = +state{0}
Column(Spacing(16.dp)) {
  Container() {
    Column() {
        text = "Counter: ${count.value}",
        modifier = Spacing(8.dp)
        text = "Increase", 
        onClick = { 
Microsoft’s .NET Multi-platform App UI (MAUI)

.NET MAUI is part of .NET 6, expected for November 2021. Microsoft calls its implementation of declarative front-ends “Model-View-Update” (MVU).

Here’s what I think the SwiftUI sample from above looks like in MVU. I adapted the sample from the announcement post:

readonly State<int> count = 0;

View body() => new StackLayout {
  new Label( "Counter: {count}" ),
  new Button(
    () => $"Increment",
    () => count.Value ++
Facebook’s React

For comparison, here’s what the counter looks like in Facebook’s React for web applications. I adapted it from this Stackblitz sample. React isn’t declarative like the other frameworks, but it comes close:

class App extends React.Component {
  state = {
    counter: 0

  render() {
    return <div>
      <p>Counter: {this.state.counter}</p>
      <button onClick={
        () => this.setState({ 
            counter: this.state.counter + 1 
Notable Flutter Plugins

Getting Started

React & JavaScript

The React website is a good starting point. React uses JavaScript to create web applications.

Learning JavaScript
Learning React
Flutter & Dart

The Flutter website is a good place to get familiar with Flutter. Flutter uses the Dart programming language to create natively-compiled applications for mobile, web & desktop. Both Flutter and Dart can use plugins that have a great portal.

Learning Dart

You start with the Dart language tour. Java developers take the “Intro to Dart for Java Developers” next. Then you have options:

Installing Flutter

Here are the instructions, straight from the Flutter website:

Learning Flutter

Here’s a selection of Flutter tutorials and courses:

Making Of

Third Time’s the Charm?

This is the third time that I gave this talk: The first time was at the LJC Unconference 2020, the second time at the Cincinnati JUG. So I was familiar with it and went from about 50 minutes at the Cincinnati JUG to 41 minutes this time around.

But that’s not enough: For my JavaLand talk, I need to get this down to 35 minutes - in German. So I need to cut nearly 10 minutes because I also want to add some things. 😓

The Summary Stash

I used the “Summary Stash” for the first time ever in a talk. And probably for the last time! But what is that? And why won’t I do this again?

The “Summary Stash” is a slide where I collect miniature versions of important slides for my wrap-up. Since I use Apple Keynote’s Magic Move, it really is a miniature version, not a picture. Here’s an example:

Then at the end, I went through the stash, one slide at a time:

Well, it certainly looks the part. So why won’t I use it again? Three reasons:

  • It takes a lot of time in the talk. Between filling the “Summary Stash” and going through it at the end, it takes four minutes in total. Remember, I need to cut nearly ten minutes out!
  • I show & talk at the same time. Although my audience has seen the slides before, I still need to give them time to read the slide again. In this talk, I didn’t, violating the “Don’t show & tell at the same time” rule of talks.
  • It’s a lot of work to keep the different versions of the “Summary Stash” slide up-to-date. I did change some slides which I then needed to fix on dozens of “Summary Stash” instances.

I have an idea how I could replace the “Summary Stash”, but I’m not sure if will do this.

Out Of Sync

When you give a talk, you have three options to sync-up what your audience sees and hears:

  1. Show first, then tell: You show your point first on the slide, then talk about it.
  2. Show & tell: You show your point on the slide and talk about it at the same time. You see this most often, but you shouldn’t do this: People can’t listen and read at the same time, so they either don’t listen to you while reading - or don’t read what you’re showing.
  3. Tell first, then show: You talk about it your point first and then show it on the slide. That’s what I did here most of the time.

Here’s an example - I talk about a point before it appears on the slide:

This is the second time I did it. And the last time. Why?

  • As my wife pointed out when I told her about my talk, it’s confusing to the user. They see a point on the slide while I’m already talking about the next one. Think about subtitles in movies: You see the subtitles first, then you hear the dialog. Listening to your wife is always a good idea. Here it was an especially good one. I only wish I had asked my wife earlier!
  • It’s harder to talk about an upcoming point with in your presentation program. Instead of looking at the same screen/content that your audience sees, you need to look at the next screen - on a second screen.

So I’ll go back to option #1 - show first, then tell.

Eyes Up Here!

I always say that you should look directly into the camera in an online talk. Well, where did I look? Not into the camera! Why?

I don’t use the web cam of my Mac. Instead, I use my iPhone with the Reincubate Camo software. And I clearly put it into the wrong place this time. It also didn’t help that the “next slide” that I was talking about was on the right side of my screen (from the audience’s perspective).

I definitely need to record myself before my next talk!

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Part 9 of 9 in the Talks series.
CinJUG: "How Should Java Developers Build Front-Ends for Web, Mobile, and Desktop Today?" » | Start: LJC Lightning Talk: Eclipse OpenJ9: Memory Diet for Your JVM Applications

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