ClassPool pool = ClassPool.getDefault(); CtClass ctClass = pool.get("com.example.MyClass"); CtClass ctClass = pool.get("com.example.MyClass"); CtMethod ctMethod = ctClass.getDeclaredMethod("myMethod"); ctMethod.insertBefore("{ System.out.println(\"Entering myMethod\"); }"); ctMethod.insertAfter("{ System.out.println(\"Exiting myMethod\"); }"); ctClass.writeFile(); Class<?> optimizedClass = ctClass.toClass(); Object instance = optimizedClass.newInstance(); Method optimizedMethod = optimizedClass.getDeclaredMethod("myMethod"); optimizedMethod.invoke(instance);