Concurrent and Asynchronous Programming: Loom in Java 20 and 21
summary
Loom introduces virtual threads (preview in JDK 20, intended final in JDK 21), structured concurrency (structured-task scopes for join/timeout semantics) and scoped values (immutable alternatives to thread‑locals). The talk shows that virtual threads make creating, blocking and storing threads 100–1,000× cheaper so millions of concurrent request-handling fibers become practical, and demos replacing a Spring Boot executor with virtual threads while preserving stack traces and scaling. The project is large (about 4–5 years and ~100k lines of changes).
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chapters (9)
- 0:00Loom introduction
- 7:09Concurrent programming overview
- 12:49Blocking thread problem
- 21:41Virtual threads goals
- 29:02Advantages of blocking code
- 35:21Practical demo
- 36:23Structured concurrency
- 41:36Scope values and locals
- 46:30Java 21 roadmap
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