Enum singleton versus non-capturing lambda

[Michael Hixson]

So if I'm in that situation where the serialized form has changed,
what happens?  Deserialization throws an error?

I'm trying to convert this into general guideline I can use.
Something like:  "Only serialize lambdas into ephemeral storage.  If
you need persistent storage, use an enum instead." (?)

On Wed, Mar 13, 2013 at 6:40 PM, Brian Goetz <brian.goetz at oracle.com> wrote:
> A more apt comparison would be the serialized form of a lambda.  Which is
> probably bigger.
>
> But, the name-stability is a huge benefit.  While we've made some attempts
> to make the serialized form of lambdas stable across compilations, there are
> no guarantees.  Enums provide those guarantees.
>
>
> On 3/13/2013 8:51 PM, Zhong Yu wrote:
>>
>> On Wed, Mar 13, 2013 at 7:09 PM, Brian Goetz <brian.goetz at oracle.com>
>> wrote:
>>>
>>> Free, compact, guaranteed-stable serialization format.
>>
>>
>> It seems that the serialized format of the enum singleton is 40 bytes
>> longer than a traditional singleton, if that's a concern to anyone.
>>
>>>
>>>
>>> On 3/13/2013 8:03 PM, Zhong Yu wrote:
>>>>
>>>>
>>>> On Wed, Mar 13, 2013 at 4:51 PM, Michael Hixson
>>>> <michael.hixson at gmail.com> wrote:
>>>>>
>>>>>
>>>>> I see a couple of different forms for returning functional interface
>>>>> instances from static methods in the current lambda code.
>>>>>
>>>>> 1. Enum singleton, as in Comparators.naturalOrder()
>>>>>
>>>>>     private enum NaturalOrderComparator implements
>>>>> Comparator<Comparable<Object>> {
>>>>>       INSTANCE;
>>>>>       public int compare(Comparable<Object> c1, Comparable<Object> c2)
>>>>> {
>>>>>         return c1.compareTo(c2);
>>>>>       }
>>>>>     }
>>>>>
>>>>>     public static <T extends Comparable<? super T>> Comparator<T>
>>>>> naturalOrder() {
>>>>>       return (Comparator<T>) NaturalOrderComparator.INSTANCE;
>>>>>     }
>>>>>
>>>>> 2. Non-capturing lambda, as in Functions.identity()
>>>>>
>>>>>     public static <T> Function<T, T> identity() {
>>>>>       return t -> t;
>>>>>     }
>>>>>
>>>>> Code complexity aside, does either approach have advantages over the
>>>>> other?  Does one perform better/worse or serialize better/worse?
>>>>
>>>>
>>>>
>>>> I'd like to know too. What's the purpose of enum in the 1st example?
>>>>
>>>>>
>>>>> -Michael
>>>>>
>>>>
>>>
>