Java 24/25 Preview

StableValue is a lazy-final container that initializes at most once on first access, replacing error-prone double-checked locking with a thread-safe one-liner.

Primitive types in patterns (JEP 507) extends instanceof and switch to match primitive types like int, long, and double with safe narrowing conversions.

Module imports replace dozens of individual imports with one line, and compact source files let you write a complete Java program with just void main() and no class declaration.

Flexible Constructor Bodies allow statements before super() or this(), enabling parameter validation and computation before the parent constructor runs.

The Vector API enables SIMD parallel computation, while the KDF, PEM, and KEM APIs standardize cryptographic operations that previously required third-party libraries.

HTTP/3 in the JDK HttpClient uses the QUIC protocol (UDP-based) for 0-RTT connection setup, no head-of-line blocking, and connection migration across network changes.

The underscore _ is used for intentionally unused variable bindings in catch blocks, for-loops, lambdas, and pattern matches, eliminating IDE warnings and documenting intent.

Project Leyden reduces JVM startup from seconds to under 100 milliseconds by pre-computing class loading, linking, and JIT compilation ahead of time into a shared archive.