JDK 27 ships nine JEPs, compact object headers on by default and PQC in TLS 1.3

JDK 27 arrives with nine JEPs: five preview updates (Vector API, structured concurrency, lazy constants, primitive patterns, PEM encodings) and four final features. Compact object headers are now on by default, G1 becomes the default GC everywhere, TLS 1.3 gains post-quantum hybrid key exchange, and JFR redacts sensitive data. The release candidate slipped two weeks due to the first Critical Security Patch Update for the JDK.

• Compact object headers cut heap use 22% and CPU 8% in SPECjbb2015
• G1 is now the default GC even on single-CPU and sub-1792 MB systems
• JEP 527 adds post-quantum hybrid key exchange to TLS 1.3
• JFR redacts secrets from command-line args, env vars and system properties