Java 21 Course
The LTS that made cheap concurrency and real data modelling mainstream.
Take this course in the learning hubLessons
- Why 21 became the default LTSUnderstand the six-month cadence and why teams jumped from 8 or 11 straight to 21.
- Virtual threads finally landedWhat actually changed in the platform when JEP 444 went final, and why it matters at scale.
- Virtual thread traps to avoidThree habits from the platform-thread era that quietly destroy virtual-thread performance.
- Sequenced collections fill a 25-year gapWhy getting the last element used to need a different incantation for every collection type.
- Pattern matching for switch goes finalAfter three previews, switch on types became a real language feature in 21.
- Record patterns: destructuring arrivesMatch a record and pull its components apart in a single step, including nested ones.
- Generational ZGCZGC learned the generational trick in 21, cutting its CPU and memory cost sharply.
- Structured concurrency (preview)Treat a group of concurrent subtasks as one unit that succeeds or fails together.
- Scoped values (preview)An immutable, inheritable replacement for ThreadLocal designed for a million threads.
- String templates: the one that was withdrawnPreviewed in 21, previewed again in 22, then pulled entirely - a useful lesson about preview status.
- Unnamed patterns and variables (preview)The underscore says "something is here and I do not care", which removes a lot of noise.
- Key Encapsulation Mechanism APIA standard API for the key exchange that post-quantum cryptography depends on.
- What 21 deprecated and restrictedThree removals that can break an upgrade if you find them at deploy time instead of build time.
- Upgrading from 17 to 21A practical order of work, and the one change that gives most of the benefit.
- Virtual threads in a real serviceWhere they help, where they pin, and what they do not fix.