Returns a set view of the mappings contained in this map. Each element
in the returned set is a
Map.Entry
. The set is backed by the
map, so changes to the map are reflected in the set, and vice-versa.
If the map is modified while an iteration over the set is in progress,
the results of the iteration are undefined. The set supports element
removal, which removes the corresponding mapping from the map, via the
Iterator.remove,
Set.remove,
removeAll,
retainAll and
clear operations. It does not support
the
add or
addAll operations.
This implementation returns a CompositeSet
which
composites the entry sets from all of the composited maps.