SESSION ABSTRACTS

The Art of Java Language Pattern Matching

The goal of project Amber within OpenJDK is to explore the inclusion of smaller, productivity-oriented Java language features. One part of this that has delivered new functionality in recent versions is pattern matching.

Pattern matching is where application logic combines testing if an expression has a specific type or structure and then extracting components of its state for processing.

In JDK 14, JEP 305 introduced pattern matching for instanceof, as a preview feature and was made a full feature in JDK 16. This simplifies the use of this operator by eliminating the need for an explicit cast and assignment. In JDK 17, JEP 406 added pattern matching for switch. It is now possible to include patterns in switch case labels.

In this session, we looked at the details of these two new language features, as well as a more general look at pattern matching. We also explored future features in this area, such as record patterns (scheduled for JDK 19) and array patterns, which may be included in a subsequent Java release.

By the end of the session, our Java community were ready to make use of these powerful new features.

Java on CRaC: Superfast JVM Application Startup

One of the key benefits of a microservice architecture is the ability to dynamically respond to changes in load by spinning up new instances as required. However, when deploying JVM-based services, the warmup time of JIT compilation can be a limitation on the effectiveness of this technique.

One approach to solving this problem is using native images, where the service is statically compiled using an ahead-of-time (AOT) compiler. Although this does reduce startup time and footprint, it does so at the cost of overall performance.

A new project has been proposed and accepted into OpenJDK called CRaC (Coordinated Restore at Checkpoint). The goal is to research the co-ordination of Java programs with mechanisms to checkpoint (snapshot) a running application. Restoring from the snapshot could solve some of the problems with the startup and warmup times, especially in microservices.

In this session, we looked at the main challenges for such a project, potential solutions and the results from a proof-of-concept implementation.

About Simon Ritter Simon joined Sun Microsystems in 1996 and spent time working in both Java development and consultancy. He has been presenting Java technologies to developers since 1999 focusing on the core Java platform as well as client and embedded applications.

Simon is now the Deputy CTO of Azul Systems where he continues to help people understand Java and Azul’s JVM products. He represents Azul on the JCP Executive Committee as well as the JSR Expert Groups for Java SE 9 and later.

Find him on Twitter @speakjava

About the Dublin Java User Group

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Stackand.Co enrich the professional lives of Java / Scala software professionals - with over 20 years experience in the Irish ICT market, they have helped many great people elevate their careers.

Perhaps they can do the same for you working with companies like this one?

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Version 1 is a trusted technology partner to major domestic and international customers across all industry sectors in the UK and Ireland. Their Java practice has grown to over 120 people over the last few years, and continues to grow. Many of their Java customers use a significant amount of open-source tools and technologies, and therefore Version 1 work with the community to hear other Java success stories, learn more about people’s experiences, and bring in Java experts and champions to get the latest on what’s going on in that space.”

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Global Payments Inc makes it easy for business to accept payments online, on mobile and in-app blending global coverage, local expertise and the best possible service to help drive business growth. Headquarted in Atlanta, they have a thriving technology division based on Sir John Rogerson's Quay.

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Equifax Technology Ireland is the Research and Development arm of global credit scoring organisation Equifax - it has recently opened a technology centre in the Bloodstone Building, Dublin 2.

Now looking for developers!

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