javademos/lanes/src/UnnamedVariables.java

/**
 * "Unnamed patterns and unnamed classes are also final in 25" is only half true. Unnamed variables and patterns (the
 * underscore) were finalised in Java 22 (JEP 456). What became final in 25 is compact source files and instance main
 * methods (JEP 512), the successor to "unnamed classes". This file checks the underscore half.
 * Chapter: docs/14-lanes-21-to-25.md
 */
public class UnnamedVariables {
    record Point(int x, int y) {}

    public static void main(String[] args) {
        Object o = new Point(3, 4);
        if (o instanceof Point(int x, _)) {
            System.out.println("matched a Point, x = " + x + ", y ignored with _");
        }
        try {
            Integer.parseInt("nope");
        } catch (NumberFormatException _) {
            System.out.println("caught NumberFormatException without naming it");
        }
    }
}