JDK 27 delivers over 2,300 commits with performance improvements across libraries, garbage collectors, JIT compiler, and runtime. Key features include Compact Object Headers enabled by default, G1 as the default garbage collector, and optimizations to HashMap bulk copies, AttributedString, URL.toString(), and file I/O operations, with reported improvements ranging from 35% to 86% in specific benchmarks.
A performance benchmarking study comparing Java runtime efficiency across OpenJDK versions 8 through 27 using a Ryzen Threadripper system running Fedora, employing DaCapoBench and Renaissance benchmarks with default configurations to assess how performance has evolved over more than a decade.