JDK 25 has recently been released and is packed with performance improvements compared to JDK 21, allowing your unchanged application code to run even faster.

In this talk, we will take a closer look at 13 concrete performance improvements made between JDK 21 and JDK 25 involving both the standard Java libraries, the JIT compiler, and in garbage collectors. We will explore some of the design considerations made and how performance is evaluated by the JDK developers in a world of conflicting optimization criterion and varying platform properties.

One of the 13 improvements under the microscope is the newly introduced preview feature “Stable Value” that allows a field to share the benefits of both mutable and immutable fields simultaneously. We will learn how this new feature works, how much performance can be improved, and how your code can take advantage of it already today.

Jfokus

A conference talk by Oracle engineers covering Java performance improvements from JDK 21 to JDK 25. Topics include performance metrics (throughput, latency, startup time, warmup), JIT compiler optimizations (inlining, loop unrolling, hoisting, dead code elimination, auto-vectorization), and specific JDK improvements: late barrier expansion for G1 GC, generational ZGC now default, compact object headers (reducing object size from 96 to 64 bits, saving 4 bytes per object), and JFR method timing enhancements. Benchmarks show ~10% latency improvement just by upgrading JDK, and 24% energy reduction from JDK 8 to 25. The Leyden project (AOT cache for faster startup/warmup) is also previewed.

Java Performance Update: From JDK 21 to JDK 25, by Per Minborg