Proposal: Indexing access syntax for Lists and Maps

[Mark Thornton]

Shams Mahmood wrote:
> Hi Joe,
>
> Haven't used too many annotations in Java code. I had fiddled with the idea
> of Indexable (yes even I
> had come up with the same name - our vocabularies are so limited ;) ), but I
> decided otherwise for the
> following reasons:
>
> 1) Java traditionally has wanted to avoid operator overloading (Indexable
> means compiler providing
> operator support for Indexable marked classes). Although for each loops have
> special handling cases
> for Iterable types.
> 2) get/set implementation of Lists and Maps will need to change. In fact Map
> doesn't even have a
> set, so a new method will be added to the interface breaking backwards
> compatibility.
>
> Shams.
>
>   
The advantage of using an annotation is that the List/Map interfaces 
DON'T need to change other than the addition of the annotation to 
specify the methods to be used for indexed get and set. So Map becomes 
something like:

interface Map<K,V> {
    @indexedGet V get(Object key);
    @indexedSet V put(K key, V value);
    // rest unchanged
}

interface List<E> {
    @indexedGet E get(int index);
    @indexedSet E set(int index, e element);
}


Implementations of these interfaces don't need to change at all. A 
marker interface could be used as well, but doesn't seem to me to be 
strictly necessary (I'll post some more suggestions on this later).

Regards,
Mark Thornton