Set<String> () { final Set<String> existingMethods = new HashSet<>(); myOriginalClass.accept(new ClassVisitor(API_VERSION) { @Override public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) { existingMethods.add(name); return null; } }, ClassReader.SKIP_CODE | ClassReader.SKIP_DEBUG | ClassReader.SKIP_FRAMES); return existingMethods; }