What is pattern matching for switch in Java?

Pattern matching for switch (Java 21, finalized) extends switch expressions to match on type patterns, guard patterns, and record patterns. Example: String result = switch (obj) { case Integer i -> "int: " + i; case String s when s.length() > 5 -> "long string"; case null -> "null"; default -> "other"; };. This eliminates lengthy if-instanceof-cast chains. With sealed classes, all subtypes can be covered exhaustively. Guard patterns (when clause) add conditions beyond type matching. This is a major step towards functional-style pattern matching in Java, aligning it with modern languages like Kotlin, Scala, and Haskell.