The new "foreach" statement and maps

Question

The new "foreach" statement requires an object that implements the java.lang.Iterable<T> interface.
But why do not extend "for" for accepting objects that implements the Map interface?
Map<String,String> m = new TreeMap<String,String>();
for (String key, String value : m) {
     System.out.println (key + "=" + value);   
}The current alternative
Map<String,String> m = new TreeMap<String,String>();
for (Map.Entry<String,String> e : m.entrySet()) {
     System.out.println (e.getKey() + "=" + e.getValue());   
}is not so clean.

Answer 1

The new "foreach" statement requires an object that
implements the java.lang.Iterable<T> interface.Incidentally, I believe "foreach" also allows an object that is an array.
But why do not extend "for" for accepting objects that
implements the Map interface?I think that the use of "Iterable" is a very good idea. The interface contains just one method (iterator) and that method is inherently linked to the concept of "foreach". This means anyone can write their own class that implements Iterable, and their class can then be used with "foreach".
If we specified that "foreach" also worked with Map (with its umpteen methods, only one of which (entrySet) is relevant to "foreach"), this would prevent people writing their own classes which iterate through pairs of values (unless those classes happened to implement Map).
Ideally, there would be a new interface Pair<A,B> in java.lang (with getFirst() and getSecond() methods), and then if the compiler came across something like this:
    for (String str, Widget widget : items) { ... }where items is an instance of Iterable<Pair<String,Widget>>, then for each iteration, the "Pair" would be split into its component parts and stored in the variables "str" and "widget".
Unfortunately, it would be difficult to retrofit this concept to java.util.Map, since it would require Map to introduce a new method:
interface Map<K,V> extends Iterable<Pair<K,V>> {
    Iterator<Pair<K,V>> iterator();
}and Map.Entry would need to extend Pair, and therefore introduce two new methods:
interface Entry<K,V> extends Pair<K,V> {
    K getFirst();
    V getSecond();
}Both of these changes would break huge amounts of existing code that uses Map or Map.Entry.
Maybe one for Java 3 :)
Geoff