Java SPI: The Built-in Superpower Every Developer Should Know
There is a plugin system hiding inside the JDK that most developers never use on purpose. Java SPI (ServiceLoader) lets you add behavior without touching the code that consumes it. I show it with real code from my NES emulator, kill the fragile META-INF file with Google AutoService, cover the modern JPMS variant, and finish with how Quarkus does the same idea at build time.