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
2026-09-21 15:08:50 +00:00
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+import java.util.concurrent.StructuredTaskScope;
+
+/**
+ * The structured concurrency example from ankurm.com/java-21-to-25-lts-features. JEP 505 in Java 25 is the FIFTH
+ * PREVIEW, not a final feature: without --enable-preview javac refuses, on 25, 26 and 27 alike.
+ * Chapter: docs/14-lanes-21-to-25.md
+ */
+public class StructuredHub {
+    record Dashboard(String user, String order) {}
+
+    static String fetchUser(int id) throws InterruptedException { Thread.sleep(20); return "user-" + id; }
+    static String fetchOrder(int id) throws InterruptedException { Thread.sleep(30); return "order-for-" + id; }
+
+    static Dashboard fanOut(int userId) throws Exception {
+        try (var scope = StructuredTaskScope.open()) {
+            var user = scope.fork(() -> fetchUser(userId));
+            var order = scope.fork(() -> fetchOrder(userId));
+            scope.join();
+            return new Dashboard(user.get(), order.get());
+        }
+    }
+
+    static String firstSuccess() throws Exception {
+        try (var scope = StructuredTaskScope.open(StructuredTaskScope.Joiner.<String>anySuccessfulResultOrThrow())) {
+            scope.fork(() -> { Thread.sleep(200); return "slow"; });
+            scope.fork(() -> "fast");
+            return scope.join();
+        }
+    }
+
+    public static void main(String[] args) throws Exception {
+        System.out.println("java.version = " + System.getProperty("java.version"));
+        Dashboard d = fanOut(7);
+        Check.that(d.equals(new Dashboard("user-7", "order-for-7")), "fan-out: both results joined: " + d);
+        Check.that(firstSuccess().equals("fast"), "anySuccessfulResultOrThrow(): the first result wins and the slow subtask is cancelled");
+    }
+}