JVM Internals Overview

A few pieces of the JVM worth knowing exist, without needing to master them immediately:

• Classloading — the JVM loads .class files on demand, the first time a class is actually referenced.
• The JIT compiler — bytecode starts out interpreted, but code paths run repeatedly are compiled down to native machine code at runtime for speed (this is why a long-running JVM process often gets faster the longer it runs).
• The heap and garbage collector — several GC algorithms exist (G1, the default in modern JVMs, among others), tuned via JVM flags for different workloads.

java -Xmx512m -XX:+UseG1GC Main   # example JVM tuning flags