Preview Feature — Requires --enable-preview at compile and runtime. The _ identifier was reserved in Java 9; this JEP gives it formal semantics. The Problem: Forced Naming of Unused Things When pattern matching, you often care about only some components of a matched structure. But the syntax forces you to name everything: record Point(int x, int y) {} record ColoredPoint(Point point, String color) {} record Box(ColoredPoint cp, int weight) {} // You only care about the color — but must name everything else if (obj instanceof Box(ColoredPoint(Point(int x, int y), String color), int weight)) { System.