Java 27 and 26: runnable demos and captured output for every JEP, plus version lanes

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01B38FGKKam5SCGgwgduVAh3

lanes/src/UnnamedVariables.java

@@ -0,0 +1,21 @@
+/**
+ * "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");
+        }
+    }
+}