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All About JLS 17
JLS 17 • 2021 • Sealed classes and pattern-matching momentum
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Sealed classesPattern matchingLTS milestone

All About JLS 17

JLS 17 sits at the LTS milestone where sealed classes and pattern-matching work made the Java type system feel more expressive and more structurally aware.

Specification edition

JLS 17

JLS 17 sits at the LTS milestone where sealed classes and pattern-matching work made the Java type system feel more expressive and more structurally aware.

Sealed classesPattern matchingLTS milestone
What shifted

How the specification changed

Continued the move toward richer type relationships and clearer intent at the source-language level.

It gave developers more control over hierarchies and prepared the ground for more advanced pattern-oriented code.

Reading note

Why this edition matters

JLS 17 is one of the most practically important modern spec editions.

A strong anchor point for modern Java language design discussions.

Related pages

Continue through the language-spec path

Common JLS Return to the JLS timeline and compare this edition with neighboring spec milestones. Common Java See the broader language-release story that this specification edition belongs to. Common Class File Compare source-language evolution with the class file and JVM side of Java evolution. Compatibility Cross-check this specification milestone with Java, JDK, and runtime layers.