It’s been a long wait, but the time has finally come to start puzzling out Project Jigsaw’s JDK builds. As of  Wednesday evening, the first Early access builds for the initiative that’s bringing about a modular Java platform in SE 9 (and most likely EE 9) are available to download.

In an email to the Jigsaw mailing list, Java Chief Platform Architect Mark Reinhold writes that although a lot of ground has been covered on JSR 376, which defines an “approachable yet scalable modular system for the Java Platform,” work is far from complete.

The emphasis for this particular JSR is on making any modular version of Java easy to learn and use, and making it easy for devs to build and maintain libraries and large apps for the Java SE and Java EE platforms. With the advent of modularity, and the spring clean the platform is getting with the next update, it’s hoped that Java 9 and future updates will offer better platform integrity and improved performance.

Reinhold also published an informal overview on state of modularity in the platform, which is well worth a read for a glimpse of what Java’s future holds – even if, like many developers, you’ll only be utilising a few aspects of the modular system. Whilst advanced things like qualified exports, increasing readabilty and layers will, Reinhold speculates, remain the province of a handful of devs, over the next few years, he expects terms like “basic concepts of module declarations,modular JAR files, module graphs, module paths, and unnamed modules” will become part of the vocabulary of most Java users. 

In a follow-up mail by Oracle Quality Engineering Manager Rory O’Donnell, he writes that, with the prototype builds for Jigsaw, you’ll find the latest versions of the aforementioned JSR 376 and that of the JDK-specific APIs and tools described in JEP 261.

At this point in time, O’Donnell states that the most helpful things that early adopters can do is “Try to run existing applications, without change, on these builds to see whether the module system, or the modularisation of the platform, breaks your code or identifies code that depends upon JDK-internal APIs or other unspecified aspects of the platform.”

He encourages users to utilise the quick start guide ( to  experiment with the module system itself, and to “start  thinking about how to migrate existing libraries and application components to modules.” Oracle also hope to publish some more specific migration tips in the near future.

Going forward, the JSR 376 expert group will turn their attention to the overall design, and on specific changes and additions to the Java SE Platform Specification.

You can get your first taste of Jigsaw over at: And if you’d like to read more about Jigsaw, Java 9, and some ongoing issues with the substantial remodelling happening within the platform, we recommend checking out the following: 

Oracle Pushes Our Early Access Builds for Project Jigsaw and Modularity Overview

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