j.l.r.Parameter.hashCode() question

[Joe Darcy]

Hello Elena,

On 10/24/2013 07:37 AM, elena votchennikova wrote:
> Hello Joe,
>
> On 04.10.2013 21:14, Joe Darcy wrote:
>> Hello Elena,
>>
>> On 10/04/2013 03:49 AM, elena votchennikova wrote:
>>> Hi Joe,
>>>
>>> thank you for the replay,
>>>
>>> On 04.10.2013 5:03, Joseph Darcy wrote:
>>>> Hello Elena,
>>>>
>>>> The general requirements from Object.hashCode hold: equal objects 
>>>> must have equal hash codes. (Of necessity, unequal objects may have 
>>>> the same hash code.)
>>> Yep.
>>>>
>>>> The phrased "based on" means "some unspecified function of." It is 
>>>> generally undesirable to exactly specify a hash code function when 
>>>> you don't absolutely have to.
>>> So, do you mean that the executable and the index are just used in 
>>> this "unspecified function" or do you want to say that if the 
>>> executable and the index are same, then the hash codes will be the 
>>> same?
>>>
>>> I just want to clarify it, because if the answer is "yes" then I 
>>> think this is not obviously from the wording "based on". And if the 
>>> answer is "no", that this is Ok.
>>> But in the spec to the equals() method we have the same wording: 
>>> "Compares based on the executable and the index.". But what does 
>>> this exactly mean?
>>>
>>>
>>> Thank you for your help,
>>> Elena
>>
>> It it implicit that the hashCode and equals mehtods on Parameter 
>> follow the general hashCode and equals contract.
>>
>> Equality is based on executable and index; I don't think it is 
>> helpful to write specification that is equivalent to the 
>> implementation of
>>
>>         if(obj instanceof Parameter) {
>>             Parameter other = (Parameter)obj;
>>             return (other.executable.equals(executable) &&
>>                     other.index == index);
>>         }
>>         return false;
> I think this is not obvious from the words "Compares based on the 
> executable and the index" that Parameters are equals if 
> "other.executable.equals(executable) && other.index == index".
> If you mean exactly such check, it will be better to make the 
> documentation more strong and mention this somehow. Because different 
> implementations could weaken this contract and interpret this 
> differently. Would it be Ok?
> What do you think about it?
>

I don't really see how the equals contract saying "Compares based on the 
executable and the index" could lead a reasonable programmer to code up 
something that was not equivalent to 
"other.executable.equals(executable) && other.index == index".

I don't intend to adjust the current specification.

Cheers,

-Joe