list literal gotcha and suggestion

[Jonathan Gibbons]

+1 for the suggestion regarding HashSet.of, ArrayList.of, etc.  

This whole discussion over which type of brackets to use for which 
literal illustrates well why Java Is Not C.  Java's design point is to 
go for clarity over obscurity at the cost of typing a few more 
characters.  The fact that there can be such an ongoing discussion here 
illustrates why these literals are such a bad idea, when there are such 
clear and relatively simple alternatives.

That all being said, I think map literals *are* a good idea, just 
because there is no reasonable alternative that can be used today.  And 
even then, you really only need a syntax for a "pair", as in Expression 
":" Expression.  If you had that construct, then you could easily write 
HashMap.of(1: "1", 2: "2"), or TreeMap.of(1: "1", 2: "2"), etc

-- Jon



Stephen Colebourne wrote:
> Over the 1.4million LOC codebase I work on, I found 12 set literals.
> We're not talking about large numbers. Interestingly, the majority of
> these were constants, and may be more common than list constants.
> There weren't any cases of parameter passing of a set literal.
>
> That said, I strongly dislike the confusion apparent here. We should
> avoid new puzzlers if possible. I'd prefer
>
> List<String> list = {"1", "2", "3"} - List literal
> Map<Integer, String> list = {1 : "1", 2 : "2", 3 : "3"} - Map literal
> No set literal
> (I don't think this conflicts with the array literals...)
>
> Perhaps there is also an argument for adding the static of methods to
> construct mutable Set/List:
>
> Set<String> set = HashSet.of("1", "2", "3");  // mutable set
> List<String> list = ArrayList.of("1", "2", "3");  // mutable list
> List<String> list2 = {"1", "2", "3"};  // immutable list
>
>
> One final thought. It would be possible to add a "method" to the list literal:
>
> Set<String> set = {1, 2, 3}.toSet();  // immutable set
>
> This approach would handle additional interfaces too:
>
> SortedSet<String> set = {1, 2, 3}.toSortedSet();  // immutable sorted set
> MultiSet<String> mset = {1, 2, 3}.toMultiSet();  // immutable
> multiset/bag (if added to JDK)
>
> Stephen
>
>
> 2009/9/29 Reinier Zwitserloot <reinier at zwitserloot.com>:
>   
>> Scanning my codebase, they are quite rare. As the set literals are
>> causing rather a lot of pain, let's see some proof before going too
>> far down this road.
>>
>> Pain caused by set literals:
>>
>>  - ambiguity of {} - is that the empty set or the empty map?
>>  - set/list confusion.
>>  - the parser becomes quite a bit more complicated to handle the
>> difference between sets and maps.
>>
>>  --Reinier Zwitserloot
>>
>>
>>
>> On 2009/29/09, at 10:02, Mark Thornton wrote:
>>
>>     
>>> Reinier Zwitserloot wrote:
>>>       
>>>> new HashSet<>(["a", "b", "c"]);
>>>>
>>>> is too much effort in the rare cases where you need to initialize a
>>>> set-typed parameter? This is java, not perl. Golfing isn't the end
>>>> goal.
>>>>
>>>>         
>>> Without scanning my codebase I wouldn't expect Set parameters and
>>> fields to be rare. I use Set's quite frequently.
>>>
>>> Mark Thornton
>>>
>>>       
>>
>>     
>
>