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News September 2019

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Pop quiz: how many different garbage collectors are available for you to use in OpenJDK Java 11+? For example the G1 collector is one garbage collector, and the Serial collector is another. I'm not talking about the copying collectors in the young gen and the others in the old gen, because these are all coupled together now forming a single multi-gen collector - earlier versions of Java did allow you to mix and match some of the young gen and old gen algorithms, but that is no longer possible and choosing a collector now chooses the algorithm for all gens. Stop reading now so you can properly think it through, and answer the quiz, I am willing to bet you'll get it wrong (unless you've already seen the answer after this newsletter goes live and everyone popularizes it).

The answer is 12. This isn't some subtle trick, some hidden way of multiplying the collectors. There are 2 JVM implementations in the OpenJDK - HotSpot and OpenJ9. HotSpot has 7 collectors available and OpenJ9 has 6. That would total 13, but one of the collectors (Epsilon) is the same collector in both, resulting in 12 collectors.

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Now on to this month's tips, tools, news, articles, and those talks. And of course the tips from this month's articles and talks, as ever are extracted into this month's tips page.

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Jack Shirazi

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Last Updated: 2022-06-29
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