Collections.enumeration() WAS Warning Cleanup Day

[Rémi Forax]

I've started to remove warnings from java.util
and I'm not able to cleanly retrofit java.util.PropertyPermission
because java.util.Collections.enumeration is wrongly typed.

PropertyPermission contains a member class that define
a PermissionCollection that store/load only PropertyPermissions.
One method of PermissionCollection returns an Enumeration
of Permission by calling Collections.enumeration.
But Collections.enumeration doesn't use a wildcard.

This is the actual code of Collections.enumeration is
public static <T> Enumeration<T> enumeration(final Collection<T> c) {
         return new Enumeration<T>() {
             private final Iterator<T> i = c.iterator();

             public boolean hasMoreElements() {
                 return i.hasNext();
             }
             public T nextElement() {
                 return i.next();
             }
         };
     }

and should be:
public static <T> Enumeration<T> enumeration(final Collection<? extends 
T> c) {
         final Iterator<? extends T> i = c.iterator();
         return new Enumeration<T>() {
             public boolean hasMoreElements() {
                 return i.hasNext();
             }
             public T nextElement() {
                 return i.next();
             }
         };
     }

I believe this change is source and binary compatible because the method
is static and a Collection<? extends T> is a super type of Collection<T>.

Rémi