java kotlin programming languages JVM

What I miss in Java, the perspective of a Kotlin developer

Java has been my bread and butter for almost two decades. Several years ago, I started to learn Kotlin; I never regretted it. Though Kotlin compiles to JVM bytecode, I sometimes have to write Java again. Every time I do, I cannot stop pondering why my code doesn’t look as nice as in Kotlin. I miss some features that would improve my code’s readability, expressiveness, and maintainability. This post is not meant to bash Java but to list some features I’d like to find in Java.

Kotlin serverless FaaS JVM performance GraalVM native

Kotlin and FaaS, an impossible union?

Some time ago, I read a post describing how to run a serverless Kotlin function on OpenFaaS. While the content is technically correct, I believe the concept itself is very wrong. Such posts can lead people to make ill-advised decisions: 'because we can' is hardly a winning strategy. in this post, I’d like to first explain why the JVM platform is a bad idea for FaaS. Then, I’ll proceed to propose alternatives to use Kotlin nonetheless. I deliberately chose not to link to the original

Rust JVM integration FFI JNI

Rust and the JVM

This is the 7th post in the Start Rust focus series. So far, we have learned the basics of Rust syntax, developed a custom Kubernetes controller, and integrated with the front-end with Wasm. I’ve been using the JVM for two decades now, mainly in Java. The JVM is an amazing piece of technology. IMHO, its biggest benefit is its ability to adapt the native code to the current workload; if the workload changes and the native code is not optimal, it will recompile the bytecode accordingly again.

security JVM hack

Changing a field's type in recent JDKs

A couple of years ago, I attended a talk of my former colleague (but still friend) Volker Simonis. It gave me the idea to dig a bit into the subject of how to secure the JVM. From the material, I created a series of blog posts as well as a talk. From that point on, I submitted the talk at meetups and conferences, where it was well-received. Because I like to explore different areas, I stopped to submit other proposals. Still, the talk is in my portfolio, and it was requested again in 2021. I ha

JVM bytecode javap Kotlin


There is a bunch of languages running on the JVM, from of course Java, to Clojure and JRuby. All of them have different syntaxes, but it’s awesome they all compile to the same bytecode. The JVM unites them all. Of course, it’s biased toward Java, but even in Java, there is some magic happening in the bytecode. The most well-known trick comes from the following code: public class Foo { static class Bar { private Bar() {} } public static void main(String... arg

JVM security Spring Boot policy

Proposal for a Java policy files crafting process

This is the 2nd post in the JVM Security focus series. I’ve already written about the JVM security manager, and why it should be used - despite it being rarely the case, if ever. However, just advocating for it won’t change the harsh reality unless some guidelines are provided to do so. This post has the ambition to be the basis of such guidelines. As a reminder, the JVM can run in two different modes, standard and sandboxed. In the former, all API are available with no restriction; i

JVM language

Do we need other languages on the JVM?

It seems a trend has caught on and accelerated recently: every organization worth his salt in the Java ecosystem feels the need to create its own language that runs on the Java Virtual Machine. Side by side with legacy languages like Jython and JRuby, and along more promoted ones like Scala, Red Hat announced Ceylon and now it’s JetBrain’s turn with Kotlin. However, the real question is not whether we need them (the answer is a simple 'no' since we created software without them), but