In this Foojay Podcast, we're exploring a critical topic that's becoming increasingly important in our industry: developing sustainable software that is both performant and environmentally friendly.

At the Devoxx and JFall conferences, I had fascinating conversations about how we as Java developers can make a real impact on both our cloud costs and our carbon footprint. And it's interesting to learn how these two goals are often perfectly aligned: what's good for your budget is usually good for the planet too.

We start with Daniel Witkowski. He published an article on Foojay that takes us on a deep dive into performance tuning. He explains why optimizing your code can have a thousand times more impact than saving 30% on cloud costs, and walks us through his journey of turning a simple integer validation challenge into a masterclass on Java performance optimization.

Next, I caught up with Ko Turk, who shares his passion for sustainable engineering and space exploration. He introduces us to Kepler, a tool for monitoring the energy consumption of your applications, and explains how performance optimization naturally leads to sustainability improvements.

Then Ronald Dehuysser, founder of JobRunr, reveals how his open-source job-scheduling library now enables carbon-aware job processing. He explains how JobRunr can automatically schedule non-time-critical jobs to run when renewable energy is most available.

And finally, Jan Ouwens joins us to discuss practical strategies for reducing both costs and CO2 emissions in your applications. He explains why cloud spending is actually a good proxy for your carbon footprint.

00:00 Introduction of topic and guests

02:07 Daniel Witkowski

• https://www.linkedin.com/in/danielwitkowski
• https://foojay.io/today/the-art-of-performance-tuning-why-saving-30-in-the-cloud-means-nothing-if-your-code-wastes-1000x-more/
• https://foojay.io/today/foojay-podcast-83/
• Why Saving 30% in the Cloud Means Nothing if Your Code Wastes 1000× More
• Performance tuning is less about syntax and more about craftsmanship.

29:46 Ko Turk

• https://www.linkedin.com/in/ko-turk-b271b929/
• https://github.com/sustainable-computing-io/kepler
• Sustainable engineering
• Kubernetes Efficient Power Level Exporter (Kepler)

32:46 Ronald Dehuysser

• https://www.linkedin.com/in/ronalddehuysser/
• https://www.jobrunr.io/en/
• Carbon-aware job processing with JobRunr
• Growing from an open-source project to a company

37:36 Jan Ouwens

• https://www.linkedin.com/in/janouwens/
• https://jqno.nl/
• Reducing the cost and CO2-emissions of your application
• Private cloud versus cloud providers

45:14 Outro

Welcome to another episode of the Foojay Podcast! Just like in the previous episode, I bring you conversations from two of Europe's premier Java conferences - Devoxx in Belgium and JFall in the Netherlands.

At these conferences, I had the opportunity to speak with members of the Java community about topics ranging from the evolution of Java itself to mobile development, performance optimization, and even automotive security.

My first guest is Johan Vos, a Java Champion who takes us on a journey through Java's history - from porting Java to Linux in 1995 to his current work on bringing Java and JavaFX to mobile and embedded devices through the Java On Mobile project.

Then we'll hear from Stephen Chin, author of "The Definitive Guide to Modern Java Clients with JavaFX," who shares insights on building cross-platform client applications and reflects on how his daughter has followed in his footsteps to become a published author and technology educator.

From JFall, Joseph Phillips joins us to discuss Java's evolution, the differences between REST and gRPC, and whether virtual threads have replaced the need for async implementations in modern Java applications.

Next, François Martin walks us through the world of Java performance benchmarking with JMH - the Java Microbenchmark Harness - and explains why it's so valuable for comparing different implementations and optimizing code.

Wouter De Geus shares his inspiring journey from finance and mathematics into Java development, and how his employer, the Dutch Tax Authority, supports open-source contributions and the Java community.

And finally, Roald Nefs demonstrates something truly unique - using Java and the Foreign Function & Memory API to hack into automotive systems, revealing important security considerations for both hardware and software.

Content

00:00 Introduction of topics and guests

02:11 Johan Vos

• https://www.linkedin.com/in/johanvos/
• History of Java on Linux
• How the Java language and runtime are stable and evolving at the same time
• Looking at the future of Write-Once-Run-Everywhere with Java(FX) on Mobile
• https://openjdk-mobile.github.io/

19:04 Stephen Chin

• https://www.linkedin.com/in/steveonjava/
• Author of "The Definitive Guide to Modern Java Clients with JavaFX"
• Cassandra Chin: https://www.linkedin.com/in/cassandra-chin-developer/
• Her book: https://www.amazon.nl/Raising-Young-Coders-Teaching-Programming/dp/B0DVBQZ483

23:22 Joseph Phillips

• https://foojay.social/deck/@infosec812
• Java evolutions, community
• REST versus gRPC
• Do we still need async or are virtual threads a better solution?

27:49 François Martin

• https://www.linkedin.com/in/fran%C3%A7oismartin
• Tools, chaos testing, Toxyproxy
• Java performance micro benchmarks with jmh
• https://github.com/openjdk/jmh

33:30 Wouter De Geus

• https://www.linkedin.com/in/wadegeus/
• Moved from finance to software development
• Contributing back to the open-source community

39:33 Roald Nefs

• https://www.linkedin.com/in/roaldnefs/
• Hacking cars with the FFM API
• Hardware and software security concerns
• What you can learn from the Java community

46:29 Outro

In this Foojay Podcast, we're diving deep into some of the most exciting developments happening within the OpenJDK and TornadoVM projects.

At the Devoxx and JFall conferences, we spoke with several speakers and visitors about some of the major themes that are shaping the future of Java development. The first guest is Moritz Halbritter from the Spring Engineering team. He provides us with more insights into Project Leyden and how it's improving Java startup times through ahead-of-time compilation and profiling. We'll learn how Spring Boot developers can already take advantage of these improvements today.

Next, we'll hear from John Cecerralli at Azul about performance optimizations, the evolution from x86 to ARM64 architectures, and how OpenJDK Projects bring improvements to the JVM itself at levels we couldn't achieve before.

Then, Balkrishna Rawool will guide us through the world of vector databases and explain how Java's Vector API from Project Panama is perfectly positioned for AI use cases, despite its development beginning years before the current AI boom.

And finally, we'll meet some of the team members behind TornadoVM - Christos Kotselidis and Michalis Papadimitriou from the University of Manchester - who will explain to us how Java developers can now harness the power of GPUs for AI workloads, running large language models in pure Java without leaving the Java ecosystem. They also explain the connection between TornadoVM and the OpenJDK Project Babylon.

00:00 Introduction of topics and guests

01:58 Moritz Halbritter

* https://www.linkedin.com/in/moritz-halbritter-9301a1b1/

* Project Leyden and how it can already be used with Spring

* Difference between the approach of Project Leyden and CRaC

11:02 John Cecerralli

* https://www.linkedin.com/in/john-ceccarelli-95b7041/

* OpenJDK evolutions in Project Leyden

* Startup time improvements in Azul Prime

* Java performance

* ARM Graviton

17:08 Balkrishna Rawool

* https://www.linkedin.com/in/balkrishnarawool/

* Vector API, project Panama

22:44 Christos Kotselidis, Michalis Papadimitriou

* https://www.linkedin.com/in/michalis-papadimitriou/

* https://www.linkedin.com/in/kotselidis/

* https://www.tornadovm.org/

* https://www.tornadovm.org/gpullama3

* https://github.com/beehive-lab/TornadoVM

* TornadoVM status update, Java on GPU

* How TornadoVM relates to Project Babylon and Project Panama

33:42 Outro

On September 19th, 2025, the first AI4Devs conference (https://amsterdam.ai4devs.io/) took place in Amsterdam. I grabbed my camera and microphone to talk with speakers and attendees about the revolution in AI-powered coding and application development. In this first part, we'll explore Spring libraries, security, infrastructure and scaling, real-world use cases, event streaming, JetBrains tools, and more...

I asked all my guests the same opening question: 'What's your name, and what brings you to this conference?' Let's get started!

00:00 Introduction

00:44 Christian Tzolov and Josh Long
Spring AI, Spring MCP, Spring Security
https://www.linkedin.com/in/joshlong/
https://www.linkedin.com/in/tzolov/

17:07 Brian Vermeer
AI and security and the responsibility of the developer
https://www.linkedin.com/in/brianvermeer/

27:57 Camille Nigon and Maarten Vandeperre
Quarkus, Scaling AI applications, the cost of using LLMs
https://www.linkedin.com/in/camille-nigon/
https://www.linkedin.com/in/maarten-vandeperre/

36:15 Luca Berton
Infrastructure for AI applications
https://www.linkedin.com/in/lucaberton/
https://www.youtube.com/@BertonLuca

41:15 Soham Dasgupta
Real life AI use cases
https://www.linkedin.com/in/dasguptasoham/
https://github.com/marketplace?type=models

48:03 Mary Grygleski
Event driven agents to handle complex flows
https://www.linkedin.com/in/mary-grygleski/

55:04 Anton Arhipov
Java and Kotlin at JetBrains, Junie AI
https://www.linkedin.com/in/antonarhipov/

01:06:07 Outro

Episode 78 of the Foojay Podcast. All info, show notes, and links are available at https://foojay.io/today/category/podcast/.

We're excited to present the first episode of the Foojay Podcast's fifth season, marking the release of OpenJDK 25!

For the first time, an OpenJDK release is aligned with the year, and we can welcome release 25 in 2025. As usual in the release podcast, I have my regular guest, Simon Ritter. And in this episode, we are joined by Balkrishna Rawool to talk about all the new features in this new OpenJDK version.

Guests

Simon Ritter
https://www.linkedin.com/in/siritter/
Balkrishna Rawool
https://www.linkedin.com/in/balkrishnarawool/

Content

00:00 Introduction of topic and guests
01:21 How important is release 25 and upgrading your runtimes?
https://jdk.java.net/25/
06:00 Process of releasing a new OpenJDK version and looking forward to version 26
08:16 What are JEPs and OpenJDK projects
09:20 Project Leyden
https://openjdk.org/projects/leyden/
JEP 514: Ahead-of-Time Command-Line Ergonomics
https://openjdk.org/jeps/514
JEP 515: Ahead-of-Time Method Profiling
https://openjdk.org/jeps/515
11:28 Leyden compared to other solutions
16:21 Project Valhalla
https://openjdk.org/projects/valhalla/
17:06 JEP 519: Compact Object Headers
https://openjdk.org/jeps/519
17:40 JEP 508: Vector API (Tenth Incubator)
https://openjdk.org/jeps/508
18:58 Why Vector API is taking a long time to get finalized
21:04 JEP 502: Stable (Immutable) Values
https://openjdk.org/jeps/502
23:17 Project Loom
https://openjdk.org/projects/loom/
23:30 JEP 506: Scoped Values
https://openjdk.org/jeps/506
24:13 JEP 505: Structured Concurrency (Fifth Preview)
https://openjdk.org/jeps/505
29:22 How Java evolved over 30 years
33:34 Project Amber
https://openjdk.org/projects/amber/
34:28 JEP 507: Primitive Types in Patterns, instanceof, and switch (Third Preview)
https://openjdk.org/jeps/507
35:59 JEP 512: Compact Source Files and Instance Main Methods
https://openjdk.org/jeps/512
37:36 JEP 511: Module Import Declarations
https://openjdk.org/jeps/511
38:36 JEP 513: Flexible Constructor Bodies
https://openjdk.org/jeps/513
39:12 What's next in Project Amber
43:25 What you can learn from JEPs, OpenJDK projects, and mailing lists
44:21 JEP 521: Generational Shenandoah
https://openjdk.org/jeps/521
Trash Talk by Gerrit Grunwald
https://www.youtube.com/watch?v=xlwDe-hlSdI
48:16 JEP 510: Key Derivation Function API
https://openjdk.org/jeps/510
49:30 JEP 470: PEM Encodings of Cryptographic Objects (Preview)
https://openjdk.org/jeps/470
51:28 About Java Flight Recorder
52:27 JEP 509: JFR CPU-Time Profiling (Experimental)
https://openjdk.org/jeps/509
52:44 JEP 518: JFR Cooperative Sampling
https://openjdk.org/jeps/518
53:15 JEP 520: JFR Method Timing & Tracing
https://openjdk.org/jeps/520
53:38 More about JFR and comparing with GC logs
57:04 JEP 503: Remove the 32-bit x86 Port
https://openjdk.org/jeps/503
58:54 Looking forward to the following versions
01:00:58 Conclusion

This is the first Foojay podcast in Spanish. It's also the shortest one and the final of season 4 ;-) Jonathan Vila "highjacked" the microphone from Geertjan Wielenga (See episode 76, https://foojay.io/today/foojay-podcast-76-devbcn-report-part-1-learn-from-the-community/) during the DevBcn conference in Barcelona and interviewed a few of the participants for this first Spanish-only edition of the podcast.

Stay tuned and subscribe to the podcast in your favorite app or on YouTube. We're taking a short break and will be back in September with the launch of Java 25!

00:00 Introduction
00:39 Marlene Maldonado, DevBcn Organization
https://www.linkedin.com/in/marlene-maldonado-de-s%C3%A1
02:10 Barbara Teruggi, Speaker, Threat Modelling
https://www.linkedin.com/in/barbara-teruggi/
05:04 Santiago Rincon, CFP Member and Attendee
https://www.linkedin.com/in/santiago-rincon-martinez
07:56 Marlene Maldonado, Vicente Soriano, Volunteers
https://www.linkedin.com/in/visomar
https://www.linkedin.com/in/marlene-maldonado-de-s%C3%A1
10:25 Alvaro Navarro, Speaker, API Design
https://www.linkedin.com/in/anavarro
12:37 Vicente Cabanes, Sponsor, Grupo Castilla
https://www.linkedin.com/in/vicente-cabanes/