Update JDK features (24/25 & more) (#75)

* Add test classes and features for Java 24 and 25

- includes samples for standard features only
- adds markdown javadoc for JEPs
- organizes classes related to Java 24 and 25
- introduces `CompactSourceFile` and `JavaBaseImport` classes

* Update test classes for Java 4, 5, 12, and 15

- add new test cases for Collections API, formatted string handling, JavaBeans EventHandler, and NIO features
- improve code documentation and readability

Author: mperor

JavaReleases/src/main/java/pl/mperor/lab/java/CompactSourceFile.java

@@ -0,0 +1,8 @@
+/// Is a final top-level class in the unnamed package;
+/// Extends java.lang.Object and does not implement any interfaces;
+/// Has a default constructor with no parameters, and no other constructors;
+/// Has, as its members, the fields and methods in the compact source file; and
+/// Must have a launchable main method; if it does not, a compile-time error is reported.
+void main() {
+    IO.println("Compact source file & main method here ...");
+}

JavaReleases/src/main/java/pl/mperor/lab/java/JavaBaseImport.java

@@ -0,0 +1,10 @@
+package pl.mperor.lab.java;
+
+import module java.base;
+
+class JavaBaseImport {
+
+    private final List<String> listFromUtilPackage = List.of("a", "b", "c");
+    private final File fileFromIoPackage = new File("file.txt");
+
+}

JavaReleases/src/test/java/pl/mperor/lab/java/Java12.java

@@ -62,7 +62,7 @@ private String generateFileHashMD5(Path file) throws NoSuchAlgorithmException, I
 
         StringBuilder sb = new StringBuilder();
         for (byte b : hashBytes) {
-            sb.append(String.format("%02x", b));
+            sb.append(String.format("%02x", b)); // byte to 2‑digit hex
         }
         return sb.toString();
     }

JavaReleases/src/test/java/pl/mperor/lab/java/Java15.java

@@ -62,7 +62,15 @@ public void testTextBlock() {
 
     @Test
     public void testStringFormatted() {
-        Assertions.assertEquals("Hello World!", "Hello %s".formatted("World!"));
+        var positionInFormatted = """
+                user: %1$s
+                last name: %2$s
+                name: %1$s""".formatted("John", "Smith");
+        Assertions.assertEquals("""
+                user: John
+                last name: Smith
+                name: John""", positionInFormatted);
+
         Assertions.assertEquals("Value: 0.00", String.format(Locale.US, "Value: %.2f", 0d));
     }
 

JavaReleases/src/test/java/pl/mperor/lab/java/Java24.java

@@ -0,0 +1,54 @@
+package pl.mperor.lab.java;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+import java.util.stream.Gatherers;
+import java.util.stream.IntStream;
+
+/// Java 24 (March 2025)
+/// [JDK 24](https://openjdk.org/projects/jdk/24)
+///
+/// - STANDARD FEATURES:
+///     - 472:	Prepare to Restrict the Use of JNI
+///     - 475:	Late Barrier Expansion for G1
+///     - 479:	Remove the Windows 32-bit x86 Port
+///     - 483:	Ahead-of-Time Class Loading & Linking
+///     - 484:	Class-File API
+///     - 485:	Stream Gatherers
+///     - 486:	Permanently Disable the Security Manager
+///     - 490:	ZGC: Remove the Non-Generational Mode
+///     - 491:	Synchronize Virtual Threads without Pinning
+///     - 493:	Linking Run-Time Images without JMODs
+///     - 496:	Quantum-Resistant Module-Lattice-Based Key Encapsulation Mechanism
+///     - 497:	Quantum-Resistant Module-Lattice-Based Digital Signature Algorithm
+///     - 498:	Warn upon Use of Memory-Access Methods in sun.misc.Unsafe
+///     - 501:	Deprecate the 32-bit x86 Port for Removal
+///
+/// - PREVIEW & INCUBATOR:
+///     - 404:	Generational Shenandoah (Experimental)
+///     - 450:	Compact Object Headers (Experimental)
+///     - 478:	Key Derivation Function API (Preview)
+///     - 487:	Scoped Values (Fourth Preview)
+///     - 488:	Primitive Types in Patterns, instanceof, and switch (Second Preview)
+///     - 489:	Vector API (Ninth Incubator)
+///     - 492:	Flexible Constructor Bodies (Third Preview)
+///     - 494:	Module Import Declarations (Second Preview)
+///     - 495:	Simple Source Files and Instance Main Methods (Fourth Preview)
+public class Java24 {
+
+    @Test
+    public void testWindowFixedGatherer() {
+        var result = IntStream.rangeClosed(1, 3)
+                .boxed()
+                .gather(Gatherers.windowFixed(2))
+                .toList();
+
+        Assertions.assertEquals(
+                List.of(
+                        List.of(1, 2),
+                        List.of(3)
+                ), result);
+    }
+}

JavaReleases/src/test/java/pl/mperor/lab/java/Java25.java

@@ -0,0 +1,41 @@
+package pl.mperor.lab.java;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import pl.mperor.lab.common.TestUtils;
+
+/// Java 25 (September 2025)
+/// [JDK 25](https://openjdk.org/projects/jdk/25)
+///
+/// - STANDARD FEATURES:
+///     - 503:	Remove the 32-bit x86 Port
+///     - 506:	Scoped Values
+///     - 510:	Key Derivation Function API
+///     - 511:	Module Import Declarations
+///     - 512:	Compact Source Files and Instance Main Methods
+///     - 513:	Flexible Constructor Bodies
+///     - 514:	Ahead-of-Time Command-Line Ergonomics
+///     - 515:	Ahead-of-Time Method Profiling
+///     - 518:	JFR Cooperative Sampling
+///     - 519:	Compact Object Headers
+///     - 520:	JFR Method Timing & Tracing
+///     - 521:	Generational Shenandoah
+///
+/// - PREVIEW & INCUBATOR:
+///     - 470:	PEM Encodings of Cryptographic Objects (Preview)
+///     - 502:	Stable Values (Preview)
+///     - 505:	Structured Concurrency (Fifth Preview)
+///     - 507:  Primitive Types in Patterns, instanceof, and switch (Third Preview)
+///     - 508:	Vector API (Tenth Incubator)
+///     - 509:	JFR CPU-Time Profiling (Experimental)
+public class Java25 {
+
+    @Test
+    public void testPrintFromIOClass() {
+        var out = TestUtils.setTempSystemOut();
+        IO.println("Hello World!"); // ⇒ System.out.println("Hello World!");
+        Assertions.assertEquals("Hello World!" + System.lineSeparator(), out.all());
+        TestUtils.resetSystemOut();
+    }
+
+}

JavaReleases/src/test/java/pl/mperor/lab/java/Java4.java

@@ -2,16 +2,21 @@
 
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
+import pl.mperor.lab.common.TestUtils;
 
 import javax.imageio.ImageIO;
 import java.awt.image.BufferedImage;
+import java.beans.EventHandler;
 import java.io.*;
 import java.net.InetSocketAddress;
 import java.net.ServerSocket;
 import java.nio.channels.ServerSocketChannel;
 import java.nio.channels.SocketChannel;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.nio.file.attribute.BasicFileAttributes;
+import java.nio.file.attribute.FileTime;
+import java.time.Instant;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.Executors;
 import java.util.logging.Logger;
@@ -37,8 +42,12 @@ public void testNewInputOutputAkaNIO() throws IOException {
         Path path = Path.of("src", "test", "resources", "nio.txt");
         byte[] fileBytes = Files.readAllBytes(path);
         String content = new String(fileBytes);
-
         Assertions.assertEquals("Hello NIO!", content);
+
+        var fileCreationTime = Files.readAttributes(path, BasicFileAttributes.class)
+                .creationTime();
+        System.out.printf("📃 File '%s' - last access time: ⌚%s%n: ", path.getFileName(), fileCreationTime);
+        Assertions.assertTrue(fileCreationTime.compareTo(FileTime.from(Instant.now())) <= 0);
     }
 
     @Test
@@ -125,4 +134,17 @@ private void handleConnectedClient(ServerSocket serverSocket) throws IOException
         }
     }
 
+    @Test
+    public void testJavaBeansEventHandler() {
+        var out = TestUtils.setTempSystemOut();
+        Runnable runnable = EventHandler.create(Runnable.class, this, "run"); // () -> run();
+        runnable.run();
+        Assertions.assertEquals("Run was called!", out.all());
+        TestUtils.resetSystemOut();
+    }
+
+    public void run() {
+        System.out.print("Run was called!");
+    }
+
 }

JavaReleases/src/test/java/pl/mperor/lab/java/Java5.java

@@ -8,6 +8,7 @@
 import java.lang.annotation.*;
 import java.lang.reflect.Method;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.*;
 import java.util.concurrent.atomic.AtomicInteger;
@@ -146,4 +147,14 @@ public void testStringBuilderInsteadOfStringBuffer() {
         Assertions.assertEquals("Hello World", sb.reverse().toString());
     }
 
+    @Test
+    public void testCollectionsAPI() {
+        var collection = List.of(1,2,3,2,2);
+        Assertions.assertEquals(3, Collections.frequency(collection, 2));
+
+        List<String> empty = Collections.emptyList();
+        Assertions.assertNotNull(empty);
+        Assertions.assertTrue(empty.isEmpty());
+    }
+
 }