Groups > comp.lang.java.programmer > #34304

Re: hashtables syntax

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From	Steven Simpson <ss@my.domain.invalid>
Newsgroups	comp.lang.java.programmer
Subject	Re: hashtables syntax
Date	Mon, 16 May 2016 15:51:59 +0100
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On 16/05/16 12:48, Eric Sosman wrote:
> On 5/16/2016 1:26 AM, ruben safir wrote:
>> Gotchya, but it seems inconsistent.
>>
>>
>> why not like
>>
>> HashMap<> function = new HashMap<String, Type[]>
>
>     With what is this "inconsistent?"  I'm not seeing your point.
>
>     The types must be specified on one side or the other; Java
> decided to insist that they appear on the left.  Java *could*
> have chosen to have them on the right (I suppose, but there may
> be considerations I'm unaware of), but it chose the left.  Shrug.

It would arguably be inappropriate to put the type information 'on the 
right' in the the OP's case, where the declaration of the reference is 
separate from its assignment.  The generic parameters would be visible 
only within the static initializer, while the declaration is visible 
throughout.  Imagine:

    private static HashMap<> functions;

     static { // initialize function types
         functions = new HashMap<String, Type[]>();

Compile-time checking of calls like functions.get(20) would have to 
inspect the static initializer, rather than the declaration.  Also, I 
expect it would be more complex to inspect situations like this:

    private static HashMap<> functions;

    // at some point
    functions = new HashMap<String, Type[]>();

    // later
    functions = new HashMap<Integer, String>();

The declaration acts as a kind of rendezvous point between users and 
providers of 'function', so it makes sense to propagate type information 
out from that point.

-- 
ss at comp dot lancs dot ac dot uk

Thread

hashtables syntax Popping mad <rainbow@colition.gov> - 2016-05-15 06:31 +0000
  Re: hashtables syntax Lew <lewbloch@gmail.com> - 2016-05-14 23:52 -0700
    Re: hashtables syntax Popping mad <rainbow@colition.gov> - 2016-05-15 10:23 +0000
      Re: hashtables syntax Lew <lewbloch@gmail.com> - 2016-05-15 09:33 -0700
        Re: hashtables syntax Lew <lewbloch@gmail.com> - 2016-05-15 09:35 -0700
      Re: hashtables syntax Eric Douglas <e.d.programmer@gmail.com> - 2016-05-16 06:10 -0700
  Re: hashtables syntax Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-05-15 07:44 -0400
    Re: hashtables syntax ruben safir <ruben@mrbrklyn.com> - 2016-05-16 01:26 -0400
      Re: hashtables syntax Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-05-16 07:48 -0400
        Re: hashtables syntax Steven Simpson <ss@my.domain.invalid> - 2016-05-16 15:51 +0100
          Re: hashtables syntax Steven Simpson <ss@my.domain.invalid> - 2016-05-16 22:35 +0100
      Re: hashtables syntax Lew <lewbloch@gmail.com> - 2016-05-16 16:10 -0700
  Re: hashtables syntax Andreas Leitgeb <avl@logic.at> - 2016-05-15 13:43 +0000
  Re: hashtables syntax Roedy Green <see_website@mindprod.com.invalid> - 2016-05-20 18:00 -0700

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