import javassist.ClassPool; import javassist.CtClass; import javassist.CtField; import javassist.NotFoundException; public class JavassistExample { public static void main(String[] args) { try { ClassPool classPool = ClassPool.getDefault(); CtClass ctClass = classPool.get("com.example.MyClass"); CtField field = ctClass.getDeclaredField("myField"); field.setModifiers(field.getModifiers() & ~Modifier.FINAL); ctClass.writeFile(); ctClass.toClass(); e.printStackTrace(); } } }