JEP 487: Scoped Values

Author: ibrahimatay

README.md

@@ -12,6 +12,8 @@ This repository contains Java examples that are designed to track and document t
 * [Java 24](java-24/) (March, 2025)
   * [JEP 488](java-24/src/main/java/com/ibrahimatay/JEP488PrimitiveTypesInPatternsInstanceofAndSwitch.java): Primitive Types in Patterns, instanceof, and switch
   * [JEP 495](java-24/src/main/java/com/ibrahimatay/JEP495SimpleSourceFilesAndInstanceMainMethods.java): Simple Source Files and Instance Main Methods
+  * [JEP 485](java-24/src/main/java/com/ibrahimatay/JEP485StreamGatherers.java): Stream Gatherers
+  * [JEP 487](java-24/src/main/java/com/ibrahimatay/JEP487ScopedValues.java): Scoped Values
 
 * [Java 23](java-23/) (September, 2024)
   * [JEP 455](java-23/src/main/java/com/ibrahimatay/JEP455PrimitiveTypesInPatternsInstanceofAndSwitch.java): Primitive Types in Patterns, instanceof, and switch

java-24/src/main/java/JEP485StreamGatherers.java

@@ -0,0 +1,28 @@
+import java.util.concurrent.ThreadLocalRandom;
+import java.util.stream.Gatherers;
+import java.util.stream.Stream;
+
+public class JEP485StreamGatherers {
+    public static void main(String[] args) {
+        // Stream Gatherers (JEP 485)
+        // https://openjdk.java.net/jeps/485
+
+        // Custom Intermediate Operation distinctBy
+        Stream.of("foo", "bar", "baz", "quux")
+                .gather(Gatherers.distinctBy(String::length))
+                .toList();
+
+        // Creating Fixed-size Windows
+        Stream.iterate(0, i -> i + 1)
+                .gather(Gatherers.windowFixed(3))
+                .limit(2)
+                .toList();
+
+        // Parallel Processing with selectOne
+        Stream.generate(() -> ThreadLocalRandom.current().nextInt())
+                .limit(1000)
+                .parallel()
+                .gather(Gatherers.selectOne(Math::max))
+                .findFirst();
+    }
+}

java-24/src/main/java/JEP487ScopedValues.java

@@ -0,0 +1,21 @@
+import static java.lang.ScopedValue.where;
+
+public class JEP487ScopedValues {
+    // Define a scoped value
+    private static final ScopedValue<String> USER_NAME = ScopedValue.newInstance();
+
+    public static void main(String[] args) {
+        // JEP 487: Scoped Values (Fourth Preview)
+        // https://openjdk.org/jeps/487
+
+        where(USER_NAME, "John").run(() -> {
+            System.out.println("User: " + USER_NAME.get());
+            subMethod();
+        });
+    }
+
+    public static void subMethod() {
+        // Access scoped value within a sub-method
+        System.out.println("User in subMethod: " + USER_NAME.get());
+    }
+}