Read Rust

Tag: java


I would like to share a new direction that my j4rs project took after its 0.12.0 release.

Until v0.12.0, j4rs provided to Rust applications the tools to achieve calls to the Java world. This included setting up and manage JVMs, instantiating Java Classes, making calls to Java methods, providing the means for Java to Rust callbacks etc.

The project was following solely a Rust-first approach, giving the Rust applications the ability to take advantage of the huge amount of libraries and tools existing in the Java ecosystem.

This Rust->Java only approach changed in v0.12.0. j4rs can now be used as well in Java projects that want to achieve JNI calls to Rust libraries.


It's been a long time since I properly learned a new language—computer or human. Maybe 25 years. That language was Java, and although I've had to write little bits of C (very, very little) and JavaScript in the meantime, the only two languages I've written much actual code in have been Perl and Java.

I'm a co-founder of a project called Enarx, which is written almost entirely in Rust. These days I call myself an "architect," and it's been quite a long time since I wrote any production code. In the lead-up to Christmas 2019, I completed the first significant project I've written in quite a few years: an implementation of a set of algorithms around a patent application in Java. It was a good opportunity to get my head back into code, and I was quite pleased with it.

Here are some of my thoughts on Rust, from the point of view of a Java developer with a strong object-oriented background.


I’d like to take a change for this blog and leave the more bleeding edge topics to focus on perhaps one of the most important things one can do in the Rust community: teaching new Rust developers. I’ve been thinking about how best to approach teaching Rust to those used to working with Java, in order to bring a group of developers up to speed with the language for a new project.

Java was the language I learned & abused in university, so my experience with it is somewhat anachronistic and I haven’t made any real attempt to keep up with the language. When I last wrote Java, if you wanted to pass a function as an argument, you had to declare a new interface or wrap a function in Callable<T>. Java has come along way since then. It’s added features that have a clear influence from functional programming and the ML lineage of langs. I’m talking about lambda’s, Optional types, etc. This article isn’t going to tell you to write everything in Rust, or that you need to throw out all your Java code. Java is a great language with valid use cases. I want to explore some comparisons between Java and Rust for the budding Rust programmer.


Have you heard of GraalVM? If you haven't you should check it out. It is an exciting technology, you know the kind that gets a polyglot developer going.

GraalVM is one of its kind. It is a polyglot VM developed at Oracle and apart from its polyglot capabilities it also has been proven to be quite performant and has a smaller memory footprint. It has support for building native images and some modern Java microservice frameworks like Micronaut and Quarkus support GraalVM as it provides faster startup and smaller footprint which is ideal in microservice architectures.

So what are the capabilities of GraalVM? Let us take a quick look.


In a previous post, we saw how Rust WebAssembly can be integrated into a JavaFX project using the Asmble tool. Here we look at an integration of the same functionality using the Java Native Interface (JNI). Finally, we compare the two approaches in terms of convenience and performance.

wasm java

What happens when a data collection is copied and then the new copy is changed? Does the original remain the same, or does it change too?

If you think of copying as creating a completely new object, of course you expect that any change to the new copy does not affect the original object. But if you think of copying as creating a new name for the same, single object, then you expect that any change to the object through the new name appears also when you access the same object through the old name.

Let's see how is the behavior of Python, Javascript, Java, C++, and Rust regarding the assignment operator ("=") between collection variables.

javascript python java cplusplus

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