[Java Spec Report] Re: JSR 201 enhanced-for comments

One more idea.  Is it reasonable to add an additional syntax for enhanced for 
loops that allows one to reuse an existing variable rather than always 
declaring a new one?  This would parallel traditional for loops that allow you 
to reuse an existing index variable rather than declare a new one.  Here's an 
example of what I mean:

class C {
   public static void main(String[] args) {
     String s = null;
     for (s : args) {
       if (s.equals("test")) break;
       s = null;
     }
     System.out.println(s); // Will print either "null" or "test"
   }
}

Basically, if the variable (it could even be a field, rather than a local 
variable) already exists, the compiler can still perform type safety checks to 
make sure the expression components can be assigned to the variable.

If you do decide to support something like this, you will need to consider the 
use of arbitrary expressions that denote a variable (as opposed to a value):
class C {
   public static void main(String[] args) {
     for (args[0] : args);  // Is this short for...
     /* String[] a = args;
        for (int i = 0; i < a.length; i++) {
          args[0] = a[i];
          ;
        }
     */
   }
}

Eric Blake wrote:

> Below are my comments on enhanced for loops.
> 
>>------------------------------------------------------------------------
>>
>>
>>    An enhanced for loop for the Javaâ„¢ Programming Language
>>
>>      Public Review Draft
>>
>>------------------------------------------------------------------------
-- 
Someday, I might put a cute statement here.

Eric Blake             [email protected]



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