How to Build Java Applications Today: #58


Welcome to my newsletter “How To Build Java Applications Today”! If you like it, then subscribe to it on Substack! Or read it on or Medium. Even better: Share it with people who may be interested.

Next Issue: Wednesday, January 5, 2022

My newsletter usually appears on the first Wednesday of every month.


So here’s the second issue on the monthly cadence. I spent all my time on the “Java Full-Stack Index” (see below), measuring the popularity of technologies in five areas with four data points. I planned to add a new section to the newsletter but ran out of time. Why?

I attended Devoxx UK, where I gave one talk, and W-JAX Munich, where I gave two talks ( here and here). I was on-site for both conferences. Finally!

I’m also honored to be on the Program Committee (PC) for the next QCon London. It’s my first time on a conference PC, and I’m loving it!

Apart from all my conference activities, I also worked in my own start-up. And finally, I set up my brand-new MacBook Pro 16" with M1 Max and 64 GB RAM. You know, “My computer has too much RAM!” isn’t a valid sentence in English! 😁

Anyhow, I hope to have a new section in my newsletter next month. See you then!



I’m a full-stack Java developer with 22 years of experience: Spring Boot, Angular, Flutter. I’m looking for a project in May 2022, 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!

Check out my resume & work samples

Java Full-Stack Index December 2021

What do we need to build a Java application today? A JVM language, a database, a back-end framework, a web framework, and — if we want to get fancy — a mobile app framework. So my index recommends technologies in these five areas, based on popularity, industry analysis, and my 22 years of Java experience.

Why am I measuring popularity?

  • 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.

How am I measuring popularity?

I measure popularity by systematically observing what millions of developers do. And by monitoring not one but four popularity data points across the entire technology adoption journey, I can forecast the popularity of technologies in the near future.

  • 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.
  • 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.

So what’s changed over the index from November?

  • I updated all charts for all technologies with the latest numbers. I collected those November 24–26.
  • For JVM languages, databases, and back-end frameworks, I compared the numbers of Udemy students against the ones from November. For JVM languages, I did the same for mentions in Indeed job ads. This hints at trends, but these trends need more time to become visible.
  • Both the front-end and back-end frameworks now show all technologies in the charts for the numbers of Udemy students and the mentions in Indeed job ads.
  • I corrected several typos. I barely managed to get last month’s issue out before I went off to my conferences, so I couldn’t proofread this properly then.

Java Full-Stack Index December 2021


Karsten Silz is the author of this newsletter. He is a full-stack web & mobile developer with 22 years of Java experience, author, speaker, and marathon runner. Karsten got a Master’s degree in Computer Science at the Dresden University of Technology (Germany) in 1996.

Karsten has worked in Europe and the US. He co-founded a software start-up in the US in 2004. Karsten led product development for 13 years and left after the company was sold successfully. He co-founded the UK SaaS start-up “ Your Home in Good Hands” as CTO in 2020. Since 2019, Karsten also works as a contractor in the UK.

Karsten has this newsletter, a developer website, and a contractor site. He’s on LinkedIn, Twitter, and GitHub. Karsten is also an author at InfoQ.

Originally published at on December 7, 2021.




Karsten Silz is a full-stack web & mobile developer with 23 years of Java experience, author, speaker, and contractor.

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Karsten Silz

Karsten Silz

Karsten Silz is a full-stack web & mobile developer with 23 years of Java experience, author, speaker, and contractor.

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