add demo for class file

pom.xml

@@ -11,6 +11,7 @@
     <properties>
         <maven.compiler.source>21</maven.compiler.source>
         <maven.compiler.target>21</maven.compiler.target>
+        <kotlin.version>2.1.20</kotlin.version>
     </properties>
 
     <dependencies>
@@ -26,18 +27,88 @@
             <artifactId>gson</artifactId>
             <version>2.11.0</version>
         </dependency>
+        <dependency>
+            <groupId>org.jetbrains.kotlin</groupId>
+            <artifactId>kotlin-stdlib-jdk8</artifactId>
+            <version>${kotlin.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.jetbrains.kotlin</groupId>
+            <artifactId>kotlin-test</artifactId>
+            <version>${kotlin.version}</version>
+            <scope>test</scope>
+        </dependency>
 
     </dependencies>
 
     <build>
         <plugins>
+            <plugin>
+                <groupId>org.jetbrains.kotlin</groupId>
+                <artifactId>kotlin-maven-plugin</artifactId>
+                <version>${kotlin.version}</version>
+                <executions>
+                    <execution>
+                        <id>compile</id>
+                        <phase>compile</phase>
+                        <goals>
+                            <goal>compile</goal>
+                        </goals>
+                        <configuration>
+                            <sourceDirs>
+                                <source>src/main/java</source>
+                                <source>target/generated-sources/annotations</source>
+                                <source>src</source>
+                            </sourceDirs>
+                        </configuration>
+                    </execution>
+                    <execution>
+                        <id>test-compile</id>
+                        <phase>test-compile</phase>
+                        <goals>
+                            <goal>test-compile</goal>
+                        </goals>
+                    </execution>
+                </executions>
+                <configuration>
+                    <jvmTarget>${maven.compiler.target}</jvmTarget>
+                </configuration>
+            </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
                 <version>3.8.1</version>
+                <executions>
+                    <execution>
+                        <id>default-compile</id>
+                        <phase>none</phase>
+                    </execution>
+                    <execution>
+                        <id>default-testCompile</id>
+                        <phase>none</phase>
+                    </execution>
+                    <execution>
+                        <id>compile</id>
+                        <phase>compile</phase>
+                        <goals>
+                            <goal>compile</goal>
+                        </goals>
+                    </execution>
+                    <execution>
+                        <id>testCompile</id>
+                        <phase>test-compile</phase>
+                        <goals>
+                            <goal>testCompile</goal>
+                        </goals>
+                    </execution>
+                </executions>
                 <configuration>
-                    <source>{maven.compiler.source}</source>
+                    <source>${maven.compiler.source}</source>
                     <target>{maven.compiler.target}</target>
+                    <release>21</release>
+                    <compilerArgs>
+                        <arg>--enable-preview</arg>
+                    </compilerArgs>
                 </configuration>
             </plugin>
         </plugins>

src/main/java/Main.java

@@ -1,3 +1,5 @@
+package main.java;
+
 public class Main {
     public static void main(String[] args) {
         System.out.println("Hello, World!");

src/main/java/VarHandlerDemoRunner.java

@@ -1,3 +1,5 @@
+package main.java;
+
 import jvm.VarHandleDemo;
 
 import java.lang.invoke.MethodHandles;

src/main/java/jvm/classfile/TestClass.java

@@ -0,0 +1,13 @@
+package jvm.classfile;
+
+/**
+ * Compile for examine class file
+ */
+public class TestClass {
+
+    private int m;
+
+    public int inc() {
+        return m+1;
+    }
+}

src/main/java/jvm/classfile/TestClassK.kt

@@ -0,0 +1,9 @@
+package jvm.classfile
+
+class TestClassK {
+    private var m: Int = 0;
+
+    fun inc() : Int {
+        return m + 1
+    }
+}