Java 21 is in Rampdown Phase One since the beginning of June, which means the feature set is frozen. The target date for general availability is September 19, 2023. It will be the next LTS version after Java 17 released in September 2021.

Teams usually update Java from one LTS version to another, skipping non-LTS releases, and our team is no different here. And since the Java 21 feature set is frozen now, I was curious which features will be available in Java 21 since Java 17.

This means not only new features in Java 21 itself but also features delivered in Java 18, 19, and 20.

The diff between the latest and planned LTS versions.

The delta... Okay, what am I talking about? Here is the code:

javaVersions.stream()
        .filter(v -> v.version() > 17)
        .filter(v -> v.version() <= 21)
        .flatMap(v -> v.features().stream())
        .toList()

So, here is the list of all JDK Enhancement Proposals (JEPs), which were targeted into Java 18-21 plus some related JEPs from Java 17 (42 JEPs total) grouped by the feature name and the feature state in Java 21.

Features in each table go in order of my personal preference as a developer, meaning the higher row indicates the higher chances I would use this feature in my daily work.

Production-ready features in Java 21

Preview features in Java 21

Incubator features in Java 21

Experimental features in Java 21

Note

There are also changes in JDK that have no specific JEPs, but they are not covered in this post.

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