Before I ran off and created an IdeaExchange post I thought I'd run an idea past the great minds here and make sure I'm not overlooking obvious work-arounds!
I'd really like to create some reusable extensions to Apex functionality, such as a multimap implementation, where the same code could work with arbitrary objects while maintaining good type safety for each specific instance.
With Java-style generics, I could, for example, declare a class like:
public with sharing class MultiMap<K,V> { foo... }
The "<K,V>" would be the variable types used for the multimap's key and value data, perhaps implemented as Map<K,Integer> and List<List<V>>, respectively (map ties keys to the index of the outer list).
Instantiating a multimap would be as easy as:
MultiMap<String,Contact> myVar = new MultiMap<String,Contact>{};
Because that instance uses concrete object types (String and Contact), all data passed to or returned from the multimap would be automatically checked (and cast, if appropriate).
The only alternative I can see would be defining something like:
