Added Java "Unnamed Classes and Instance Main Methods" example.

Author: ianbrandt

build-logic/src/main/kotlin/org.sdkotlin.buildlogic.kotlin-project.gradle.kts

@@ -21,13 +21,6 @@ dependencies {
 
 tasks {
 
-	withType<JavaCompile>().configureEach {
-		with(options) {
-			release = javaTargetVersion.toInt()
-			isFork = true
-		}
-	}
-
 	withType<KotlinCompile>().configureEach {
 		compilerOptions {
 			optIn.addAll(
@@ -44,4 +37,20 @@ tasks {
 			)
 		}
 	}
+
+	withType<JavaCompile>().configureEach {
+		with(options) {
+			release = javaTargetVersion.toInt()
+			compilerArgs.add("--enable-preview")
+			isFork = true
+		}
+	}
+
+	withType<Test>().configureEach {
+		jvmArgs("--enable-preview")
+	}
+
+	withType<JavaExec>().configureEach {
+		jvmArgs("--enable-preview")
+	}
 }

subprojects/kotlin-for-java-devs/src/main/java/org/sdkotlin/intro/java/_00_classes/ClassesInJava.java

@@ -7,7 +7,7 @@ public class ClassesInJava {
 }
 
 // You can have multiple classes in a file, but only one public class,
-// and curly braces required.
+// and curly braces are required.
 
 class Class {
 

subprojects/kotlin-for-java-devs/src/main/java/org/sdkotlin/intro/java/_02_helloworld/HelloJava21.java

@@ -0,0 +1,12 @@
+/**
+ * Java 21+ is previewing "Unnamed Classes and Instance Main Methods":
+ * <ul>
+ * <li><a href="https://openjdk.org/jeps/445">JEP 445 (Preview 1, JDK 21)</a></li>
+ * <li><a href="https://openjdk.org/jeps/463">JEP 463 (Preview 2, JDK 22)</a></li>
+ * <li><a href="https://openjdk.org/jeps/477">JEP 477 (Preview 3, JDK 23)</a></li>
+ * <li><a href="https://openjdk.org/jeps/495">JEP 495 (Preview 4, JDK 24)</a></li>
+ * </ul>
+ */
+void main() {
+	System.out.println("Hello World");
+}