SerializedFunction.java

@Test()
    public void save_function_works() throws Exception {

        // Addtional casting allow to mark as serilized
        Function<String, String> upper = (Function<String, String> & Serializable) x -> x.toUpperCase(); 
        
        try (ByteArrayOutputStream bos = new ByteArrayOutputStream();
             ObjectOutputStream os = new ObjectOutputStream(bos)) {

            os.writeObject(upper);

            try (ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
                 ObjectInputStream in = new ObjectInputStream(bis)) {

                Function<String, String> restoredUpper = (Function<String, String>) in.readObject();

                Assertions.assertEquals("FAAS", restoredUpper.apply("FaaS"));
            }

        }
    }