At Devoxx Belgium 2025 I discussed the idea of embedded records with a few people. The idea is to take what is great about records, and extend that to classes that represent data. This responds to a pain point in Java, where there is a bit of a cliff-edge between records and classes. While millions ...

A lot of good work has been done by the core Java team on patterns, providing new ways to explore data. The latest extension, in JEP 507, is the idea that primitive type patterns should be supported. Today I'm publishing an alternative approach. Primitive Types in Patterns, instanceof, and switch Th...

I'm going to describe a trick to get pattern patching on Optional in Java 21, but one you'll probably never actually use. Using Optional As of Java 21, Pattern matching in Java allows us to check a value against a type like an instanceof with a new variable being declared of the correct type. Patter...

How do you start a Java program? With a main method of course. But the ceremony around writing such a method is perhaps not the nicest for newcomers to Java. There has been a bit of dicussion recently about how the "on-ramp" for Java could be made easier. This is the original proposal. Here are foll...

The last time I wrote about the timezone database on this blog, the database was under threat from a lawsuit. Fortunately that lawsuit went away relatively quickly as the company involved got the message that their action was a big mistake. Unfortunately this time the mess is internal. Paul Eggert i...

The switch statement in Java is being changed. But is it an upgrade or a mess? Classic switch The classic switch statement in Java isn't great. Unlike many other parts of Java, it wasn't properly rethought when pulling features across from C all those years ago. The key flaw is "fall-through-by-defa...

Java has a number of literals for creating values, but wouldn't it be nice if we had more? Current literals These are some of the literals we can write in Java today: integer - 123, 12s, 1234L, 0xB8E817, 077, 0b1011_1010 floating point - 45.6f, 56.7d, 7.656e6 string - "Hello world" char - 'a' boolea...

The Java ecosystem is made up of many individuals, organisations and companies producing many different libraries. Some of the largest projects have long had support options where users of the project, typically corporates, can pay for an enhanced warranty, guaranteed approach to bug fixes and more....

Should you adopt Java 12 or stick on Java 11 for the next 3 years? Seems like an innocuous question, but it is one of the most important decisions out there for those running on the JVM. I'll try to cover the key aspects of the decision, with the assumption that you care about running with the lates...

TL:DR; Java is still available at zero-cost, you just need to stop using Oracle JDK and start using an OpenJDK build, such as this one or this one. The trap Java 11 has been released. It is a major release because it has long-term support (LTS). But Oracle have also set it up to be a trap (either de...

There is now a Java release every 6 months - March and September. It started with Java 9 and we're about to get Java 11. But should you jump on the release train? To answer that, we need to look at how Java's release chains are being split. Looking back at Java 8 In the olden days life was simple. T...

Moving from Java 8 to Java 11 is trickier than most upgrades. Here are a few of my notes on the process. (And here are a couple of other blogs - Benjamin Winterberg and Leonardo Zanivan.) Modules Java 9 introduced one of the largest changes in the history of Java - modules. Much has been said on the...

From Java 11 its time to think beyond Oracle's JDK. Time to appreciate the depth of the ecosystem built on OpenJDK. Here is a list of some key OpenJDK builds. This is a quick follow up to my recent zero-cost Java post OpenJDK builds In practical terms, there is only one set of source code for the JD...

The Java ecosystem has always been built on a high quality $free (zero-cost) JDK available from Oracle, and previously Sun. This is as true today as it always has been - but the new six-monthly release cycle does mean some big changes are happening. Six-monthly releases Java now has a release every ...

I use Eclipse as my Java IDE. And the new release, Photon is now out. Photon is a large release, with lots of new features. The most important is the separation of the test and main classpaths, which has always been a point of pain in the IDE. Now it just works as you would expect, and the Maven plu...

Java 9 introduced a major new feature - JPMS, the Java Platform Module System. After six months I've come to the conclusion that JPMS currently offers "negative benefits" to open source library developers. Read on to understand why. Modules for library developers Java 8 is probably the most successf...

Java 9 is obsolete in just six weeks (20th March 2018). What? You haven't upgraded yet? Well, Java 10 is only going to last six months before it is obsolete too. Update 2018-03-20: Java 10 is released. Java 9 is obsolete. Release train impact The new Java release train means that there will be a new...

This article in my series on the Java Platform Module System (JPMS) is focussed on automatic modules. JPMS was previously known as Project Jigsaw and is the module system in Java SE 9. See also Module basics, Module naming and Modules & Artifacts. Automatic modules Lets say you are in charge of Java...

This is the next article in a series I'm writing to help make sense of the Java Platform Module System (JPMS) in Java SE 9. JPMS was developed as Project Jigsaw. Other articles in the series are Module basics and Module naming. Module != Artifact If you want to grasp what JPMS modules are all about,...

The Java Platform Module System (JPMS) is soon to arrive, developed as Project Jigsaw. This article follows the introduction and looks at how modules should be named. As with all "best practices", they are ultimately the opinion of the person writing them. I hope however to convince you that my opin...

The Java Platform Module System (JPMS) is the major new feature of Java SE 9. In this article, I will introduce it, leaving most of my opinions to a follow up article. This is based on these slides. Java Platform Module System (JPMS) The new module system, developed as Project Jigsaw, is intended to...

The java.time.* API (JSR-310) was added to Java SE 8, but what has been going on since then? Java Time in Java SE 9 There are currently 117 java time issues targetted into Java SE 9. Most of these are not especially interesting, with a lot of mistakes in the Javadoc that needed fixing. What follows ...

Java has long suffered from the pain of beans. To declare a simple data class takes far too much code. At JavaOne 2016, I talked about code generation options - see the slides. Code generation of mutable and immutable beans The Java ecosystem is massive. So many libraries releasd as open source and ...

Java SE 9 is slowly moving towards the finishing line. One new feature is private methods on interfaces. Private methods on interfaces in Java 9 In Java 7 and all earlier versions, interfaces were simple. They could only contain public abstract methods. Java 8 changed this. From Java 8, you can have...

Should local variable type inference be added to Java? This is the question being pondered right now by the Java language team. Local Variable Type Inference JEP-286 proposes to add inference to local variables using a new psuedo-keyword (treated as a "reserved type name"). We seek to improve the de...