AOT class preloading

Code Comparison

// Every startup:
// - Load 10,000+ classes
// - Verify bytecode
// - JIT compile hot paths
// Startup: 2-5 seconds

// Training run:
$ java -XX:AOTCacheOutput=app.aot \
    -cp app.jar com.App
// Production:
$ java -XX:AOTCache=app.aot \
    -cp app.jar com.App

Why the modern way wins

⚡

Faster startup

Skip class loading, verification, and linking.

📦

Cached state

Training run captures the ideal class state.

🔧

No code changes

Works with existing applications — just add JVM flags.

Old Approach

Cold Start Every Time

Modern Approach

AOT Cache

JDK Support

AOT class preloading

Available

Available as a standard feature in JDK 25 LTS (JEPs 514/515, Sept 2025).

How it works

AOT class preloading caches loaded and linked classes from a training run. On subsequent starts, classes are loaded from the cache, skipping verification and linking. Combined with AOT compilation, this dramatically reduces startup time.