Oracle has released Java 27, a short-term JDK update that focuses on tightening default settings rather than introducing headline features, so developers benefit automatically without needing to change code. The release includes four production-ready enhancements and five preview features, with improvements spanning memory efficiency, garbage collection, data security and preparation for future quantum computing threats.

Among the key changes, compact 64-bit object headers are now the default rather than requiring an opt-in flag, replacing the traditional 96-bit header and delivering measured gains of 22% less heap space and 8% less CPU time in benchmark testing; Amazon and SAP already use this approach in production. Java has also switched its default garbage collector for constrained environments from Serial to the more capable G1, and introduced "post-quantum hybrid key exchange" (combining traditional ECDHE with NIST's ML-KEM algorithm) to guard against future quantum decryption of intercepted data, addressing concerns that attackers are already harvesting encrypted traffic to crack later.