Wednesday, March 31, 2021

Chasing Java's release train, from 8 to 16. Part 1: JDK 9, the last big banger ...

A lot has been said about JDK's new 6 months release cadence cycle, and arguably, this is one of the most profound decisions being made in the recent history of the language and JVM platform in general. But if you, like me and other ~60% of the Java developers out there, stuck with JDK 8, the new releases mean little to your day to day job. But the language changes, the standard library changes, the JVM changes and so does the tooling around it. More importantly, the ecosystem also changes by aggressively raising the compatibility baselines. Java in 2021 is not the same as it was in 2020, 2017 and all the more in 2014, when Java 8 has seen the light. The soon to be out JDK 17, the next LTS release, would raise the bar even higher.

So the challenge many of us, seasoned Java developers, are facing is how to stay up to date? The risk of your skills becoming outdated is real. Hence this series of the blog posts: to consolidate the changes in the language, JVM, standard library and tooling over each release, primary from the perspective of the developer. At the end, we should be all set to meet the JDK 17 fully armed. To mention upfront, we are not going to talk about incubating or preview features, nor about come-and-go ones (looking at you, jaotc). Whenever it makes sense, the feature would have a corresponding JEP link, but overall there are many changes not covered by dedicated proposals. I will try to include as much as possible but there are chances some useful features may still slip away.

With that, let us open the stage with JDK 8.


Unsurprisingly, JDK 8 does not only receive the security patches and bugfixes but gets some of the new features from the upstream. The two notable ones are:
  • Improved Docker container detection and resource configuration usage: since 8u191, the JVM is fully container-aware (see please JDK-8146115). The support is only available on Linux based platforms and enabled by default.

  • JFR backport: since 8u262, JFR is supported seamlessly (see please JDK-8223147), no need to pass -XX:+UnlockCommercialFeatures and alike anymore

Although not strictly related, thanks to the JFR backport, the latest JDK Mission Control 8 release comes very handy to everyone. Hopefully, your organization does update to the recent JDK patch releases on the regular basis and these features are already available to you.


The JDK 9 release was just huge (90+ JEPs): not only from the perspective of the bundled features, but also from the impact on the platform and ecosystem. It was 2017 but even today the groundwork established by JDK 9 still continues. Let us take a look at the major features which went into it.

The JDK 9 changeset was massive, at the same time - this is the last big bang release. We have covered most interesting pieces of it, at least from the developer's point of view. In the upcoming posts we are going to dissect other releases, one by one, and reveal the hidden gems of each.

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