PROPOSAL: 'final' without explicit type

[rssh at gradsoft.com.ua]

Also see
http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/000832.html
 for URL-s with another proposal and implementation of such feature.
and
 http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/000836.html
For detailed explanation of Neal Gafter.

//BTW, I thing submitting this a good thing and will be happy see this in
//  next Java version.


> AUTOHOR: Laau aka Marek Kozieе┌
>
> FEATURE SUMMARY:
>
> MAJOR ADVANTAGE:
> It allows people to concentrate on logic during operating on heavy
> generics and to use values which are more intuitive for them than
> variables.
>
> MAJOR BENEFIT(s):
> It allows to avoid duplicating unnecessarily types of declaration.
> It increasea concentration on 'what I've got' than on 'what type is
> that' (we decrease size by one to obtain last element index, not
> because we can do this = it's int), while for variables we still keep
> concentrate on: 'what type is that' / 'what I can put there'.
> Editing existing code to get some value is easier.
> That method can be itself multi-thread with this, but it's a far future.
> Using of Generics is easier.
>
>
> MAJOR DISADVANTAGE:
> Certainly, some people will overuse this solution.
> It might be a problem if a person does not know how to give proper
> names for values.
>
> ALTERNATIVES:
> Normal variables.
>
>
> EXAMPLES
>
> SIMPLE / ADVANCED EXAMPLE:
>   public Map<String,ArrayList<String>> readMaping(){
>     final map = new HashMap<String,ArrayList<String>>();
>     for( final row : readLine() ){
>        String key = row.get(0);
>        row.remove(0);
>        map.put(key, row);
>     }
>     return map;
>   }
>
>   public Map<String,ArrayList<String>> readMaping(){
>     final map; //compile time error
>     map= new HashMap<String,ArrayList<String>>();
>     for( final row : readLine() ){
>        String key = row.get(0);
>        row.remove(0);
>        map.put(key, row);
>     }
>     return map;
>   }
>
> public class Final {
>   static final maping = new HashMap<String, ArrayList<String>>();
> }
>
> public class Final {
>   static final maping = (Map<String,ArrayList<String>>)loadMap();
> }
>
> DETAILS
>
> SPECIFICATION: FieldDeclaration
>   FieldDeclaration would be extended to allow omitting Type
> declaration if field is final and it's directly followed by assignment
> of new class instance creation(created object type would be used), or
> of CastExpression (JLS 15.16) (ReferenceType would be used).
>
> SPECIFICATION: LocalVariableDeclarationStatement
>   (JLS 14.4) Local Variable Declaration Statements would be extended
> to allow omitting Type declaration if field is final and listed rules
> taking place:
> - VariableInitializer appears.
> - Variable is not initialized directly with null.
> - VariableInitializer type is neither primitive nor Object.
> - If VariableInitializer -Expression type is intersection type (we
> always ommit Object type in intersection), then:
>  --> If intersected types have common ancestor then this ancestor is
> used as type.
>  --> If effect of intersected types is one Interface, then this
> interface is used as type.
>  --> In other way, an error occurs.
>
>
> COMPILATION:
>   Just as today, value type only need to be determined.
>   For first implementation this solution can omit supporting
> intersections.
>
> TESTING:
> The same as final-s variables.
>
> LIBRARY SUPPORT:
> No.
>
> REFLECTIVE APIS:
> No.
>
> OTHER CHANGES:
> No.
>
> MIGRATION:
> None.
>
> COMPATIBILITY
> Only code is no forward compatible.
>
> REFERENCES
>
> http://bugs.sun.com/view_bug.do?bug_id=4459053
>
> http://bugs.sun.com/view_bug.do?bug_id=4983159
>
> http://lasu2string.blogspot.com/2009/03/final-without-explicit-type-proposal.html
>
>
>
> PS. Personally I think that consider operator is better, but I'll take
> time to improve this proposal while it's more Java-like.
>
> --
> Pozdrowionka. / Regards.
> Lasu aka Marek Kozieе┌
>
> http://lasu2string.blogspot.com/
>
>