GC Changes Across Java 9–11 Release Change JEP Java 9 G1GC becomes the default GC JEP 248 Java 9 Unified GC logging (-Xlog:gc*) JEP 271 Java 10 Parallel Full GC for G1 JEP 307 Java 10 Application Class-Data Sharing (AppCDS) JEP 310 Java 11 Epsilon: No-Op GC JEP 318 Java 11 ZGC: Scalable Low-Latency GC (experimental) JEP 333 G1GC as Default (JEP 248, Java 9) G1 (Garbage-First) replaced Parallel GC as the default on systems with ≥2 CPUs and ≥2 GB heap.

Why GC Still Matters in 2024 Even with better APIs and faster hardware, garbage collection pauses remain one of the top causes of latency spikes in Java services. A 200ms GC pause in a payment processing service is a customer-visible failure. A 50ms pause in a trading system is a missed execution window. Java 21 delivers Generational ZGC — the most capable GC Java has ever shipped — as a production-ready, non-preview feature.