Structured concurrency: still preview

Java 25 Course · lesson 9 of 16 · 4 min read

Five previews in, and the API changed again - a deliberate signal worth reading.

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Key points

  • JEP 505 is the fifth preview of structured concurrency, and the API was reshaped again in 25.
  • Task scopes moved to a factory style with joiners, replacing the earlier subclass-based shape.
  • The core idea is unchanged: subtasks live and die with the block that started them.
  • It stayed preview precisely because the team is still refining ergonomics - that is the process working.
  • Use virtual threads and executors in production today; keep structured concurrency in experiments.

An API that reshapes at its fifth preview is telling you plainly not to build production code on it.

Generational Shenandoah Primitive patterns keep previewing

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 25 Course course, and every lesson in it is listed on the Java 25 Course contents page.