Why 21 became the default LTS

Java 21 Course · lesson 1 of 15 · 3 min read

Understand the six-month cadence and why teams jumped from 8 or 11 straight to 21.

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Key points

  • Since Java 9 a release ships every six months; only some are marked LTS with years of updates.
  • 8, 11, 17, 21 and 25 are the LTS line - almost all production Java sits on one of these.
  • A non-LTS release is production-quality, but support ends when the next one lands six months later.
  • 21 was the first LTS with virtual threads and finalised pattern matching, so it was worth the jump.
  • Frameworks moved fast: Spring Boot 3.2+ shipped virtual-thread support built on 21.

Non-LTS releases are for trying features; LTS releases are what you run for years.

Virtual threads finally landed

This is a reading copy. The full lesson — with the visual explainer, the interactive lab and a Run button for the code — lives in the Java 21 Course course, and every lesson in it is listed on the Java 21 Course contents page.