Pattern Matching for switch (Java 21)

Pattern matching for switch collapses long if/else instanceof chains into a single, readable block that the compiler can also reason about. It was previewed across several releases and standardized in Java 21, so a Java 21 (or later) compiler is required for what's in this lesson. We'll cover type patterns in case labels, guards with when, the explicit case null label, record deconstruction patterns, how sealed hierarchies turn switch into an exhaustive statement the compiler checks, and the dominance rules that decide which case wins when two patterns overlap.