java generate and load class from bytecode during runtime

package reghzy.asmclass;

import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;

public class Main {

    public static final ASMClassLoader LOADER = new ASMClassLoader();

    public static void main(String[] args) {
        Class<?> clazz = generateClass();
        try {
            clazz.newInstance();
        }
        catch (InstantiationException e) {
            e.printStackTrace();
        }
        catch (IllegalAccessException e) {
            e.printStackTrace();
        }
    }

    public static Class<?> generateClass() {
        String className = "MyCustomASMClass";
        String classDescription = className; // can include packages too, using the '/' char instead of '.' (e.g my/package/MyCustomASMClass)

        ClassWriter cw = new ClassWriter(0);

        cw.visit(Opcodes.V1_6, Opcodes.ACC_PUBLIC | Opcodes.ACC_SUPER, classDescription, null,  "java/lang/Object", new String[0]);
        cw.visitSource(".dyn", null);

        // Ljava/lang/Object;
        cw.visitField(Opcodes.ACC_PUBLIC, "myField", Type.getDescriptor(Object.class), null, null).visitEnd();

        MethodVisitor ctor = cw.visitMethod(Opcodes.ACC_PUBLIC, "<init>", "()V", null, null);
        ctor.visitCode();
        ctor.visitVarInsn(Opcodes.ALOAD, 0); // load this
        ctor.visitMethodInsn(Opcodes.INVOKESPECIAL, "java/lang/Object", "<init>", "()V"); // invoke super()

        // call System.out.println("hello!")

        ctor.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
        ctor.visitLdcInsn("hello!");
        ctor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V");

        ctor.visitInsn(Opcodes.RETURN);

        ctor.visitMaxs(2, 1);

        ctor.visitEnd();

        cw.visitEnd();

        byte[] bytes = cw.toByteArray();

        return LOADER.defineClass(className, bytes);

        // try {
        //     OutputStream out = new BufferedOutputStream(new FileOutputStream(new File("F:\\TEMPPP\\MyCustomASMClass.class")));
        //     out.write(bytes);
        //     out.close();
        // }
        // catch (FileNotFoundException e) {
        //     e.printStackTrace();
        // }
        // catch (IOException e) {
        //     e.printStackTrace();
        // }
    }

    private static class ASMClassLoader extends ClassLoader {
        public ASMClassLoader() {
            super(Main.class.getClassLoader());
        }

        public Class<?> defineClass(String name, byte[] data) {
            return this.defineClass(name, data, 0, data.length);
        }
    }
}