Project Valhalla lands in JDK 28 with value types

Project Valhalla’s value types are now part of JDK 28, the first release to ship the long‑awaited feature [JVM Weekly]. Value types let developers define classes that behave like primitives—no object header, no identity, and stack allocation—so code can avoid the overhead of typical Java objects.

── What shipped ──

• Value types – custom classes that the JVM treats as flat, immutable data, enabling direct memory layout and eliminating indirection. The JDK 28 preview includes the @Value annotation and the java.lang.value package that expose the new semantics.
• Enhanced generics – the compiler now supports generic signatures that include value types, allowing collections such as List<ValuePoint> without boxing.
• Runtime support – the HotSpot VM adds a new “inline type” representation and updated garbage‑collector pathways to handle stack‑allocated data safely.

Early‑access builds show measurable speedups in numeric kernels and reduced GC pressure, confirming the performance intent of the project [JVM Weekly].

── Why it matters ──

Value types give Java a path to compete with languages that already expose primitive‑like structs, opening the door for high‑throughput workloads such as scientific simulations, data‑analytics pipelines, and low‑latency services. By reducing allocation churn, they also lower memory‑footprint, which can translate into cost savings in cloud environments. Finally, the inclusion of value types signals that the Java platform is still evolving to meet modern performance demands rather than stagnating.