Java Full-Stack Index February 2022: JVM Languages

Summary

• On your current project, keep your existing language unless that language is absolutely, really not working out for you.
• If you need to switch languages or are on a new project:
  • Use Scala if you need functional programming.
  • Use Kotlin if you really need a “more modern Java”.
  • Otherwise, use the latest Java LTS version you, your team, and your application can take.

Archive

January 2022	December 2021	November 2021

Table Of Contents

• Summary
• Archive
• Applications
• Choices
• Popularity
  • Why Popularity - and How?
  • Google Searches
  • Students at Udemy
  • Questions at Stack Overflow
  • Job Ads at Indeed
• Analysis

Applications

These recommendations are for building enterprise applications on PCs and mobile devices - forms, data grids, reports. They are not for games or media applications.

Choices

Here are the choices in alphabetical order:

• Clojure
• Apache Groovy
• Java
• Kotlin
• Scala

Popularity

Why Popularity - and How?

Picking a popular technology makes our developer life easier: Easier to learn, easier to build, debug & deploy, easier to hire, and easier to convince teammates & bosses. Popularity can make a difference in two situations: When multiple technologies score the same, you could go for the most popular one. And when a technology is very unpopular, we may not use it.

Now I look at technology popularity as a funnel from interest to learning, application, and finally to skill:

• Quantity decreases in the funnel - we’re interested in many technologies, but few end up on our resumes.
• Time increases in the funnel - it takes many months, often years, for technology to move from “interest” to “skill”.

We’re interested in the trend of the ratio between competing technologies. So we use Google searches to measure interest, Udemy course buyers to measure learning, Stack Overflow questions to measure learning & application, and mentions in Indeed job ads to measure skills.

Google Searches

Google Trends demonstrates the initial interest in a technology over time:

This link produces the chart above.

Even at 1/8 of its peak interest in 2004, Java still towers over all its JVM alternatives.

To get a better picture of the Java alternatives, here they are without Java:

This link produces the chart above.

Kotlin wins, Scala is second, Groovy third, and Clojure last. We can see the fall of Scala and the rise of Kotlin, both starting five years ago. Kotlin peaked in July 2020 and is now back to 2018 levels. Groovy’s declining for nearly three years while Clojure is for almost four years.

Students at Udemy

Udemy is one of the biggest online learning sites. They publish the number of courses and students (beyond a certain threshold). This shows how many people evaluate a technology. I compare the number of students from October vs. the current numbers. Kotlin is the baseline.

Java wins by an order of magnitude, Kotlin is second, and Scala is third. Java loses a tiny percentage against Kotlin while Scala keeps up with Kotlin. Both Groovy and Clojure don’t have enough students to cross the display threshold.

Here are the links that show the courses for all and the number of students for some:

• Clojure
• Groovy
• Java
• Kotlin
• Scala

Questions at Stack Overflow

Stack Overflow Trends shows which percentage of questions at Stack Overflow has a particular technology tag. It is a proxy for using a technology during evaluation and productive use. “More questions = better” to me.

This link produces the chart above.

Java wins, Kotlin is second, Scala third. Kotlin has been rising for five years but has only reached a fifth of Java’s question volume. Java has declined for seven years, while Scala has fallen for five years. Groove and Clojure have hovered just above zero for as long as Stack Overflow has existed.

Job Ads at Indeed

The Indeed job search is active in 63 countries representing 92% of the worldwide GDP in 2020. It demonstrates the willingness of organizations to pay for technology - the strongest indicator of popularity in my mind. I compare mentions in job ads from October (“Oct 21”) against current measurements. Kotlin is the baseline.

Java wins by an order of magnitude, Kotlin is second, Scala third. Groovy has a fifth of Kotlin’s number while Clojure is last. Kotlin is on a roll: It closed the gap to Java quite a bit and pulled away from Scala simultaneously. But let’s keep things in perspective: In the three months from October 2021 to January 2022, Java gained 45,000 mentions in job ads. That’s more than Scala has in total (39,700) and nearly as much as Kotlin’s total (52,000). Both Scala and Clojure dropped in mentions.

Please see here for details, caveats, and adjustments of the job ad mentions.

You can find the detailed search results with links here. They include breakdowns by continents:

Analysis

• Usage of Java still dominates its alternatives, often by an order of magnitude.
• The evolution speed of the Java languages has increased. So even staying with the incumbent Java makes life for us developers easier.
• If Oracle gets its will, then we’ll get a new Java LTS every two years instead of every three years. This would speed up the delivery of Java language improvements.
• Kotlin is the best Java alternative. I believe that Kotlin’s rise in popularity is in part fueled by its status as the default language for Android development.
• Scala lost its position as the #2 JVM language. In job ads, it’s still neck-to-neck with Kotlin and even comfortably ahead of it in places like North America (where it leads Kotlin 2:1). But Kotlin leads globally in job ads. And Google searches and Stack Overflow questions also trend towards Kotlin. That’s why Scala is #3 for me.
• There’s one overwriting factor that requires Scala: functional programming. If that’s your need, you have to use Scala on the JVM.
• Groovy is a has-been on the JVM: Kotlin stole its place of “hipper Java”, while Grails (Ruby-on-Rails with Groovy on the JVM) has fallen out of favor. I know that the Tiobe Index places Groovy way ahead of other JVM language alternatives to Java, but I think that view is rather exclusive to Tiobe.
• Clojure fills the niche of “Lisp on the JVM”.

Here’s my recommendation:

• On your current project, keep your existing language unless that language is absolutely, really not working out for you.
• If you need to switch languages or are on a new project:
  • Use Scala if you need functional programming.
  • Use Kotlin if you really need a “more modern Java”.
  • Otherwise, use the latest Java LTS version you, your team, and your application can take.