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Map Collection Views

I would like to know about Map  Collection Views . what are different types of it. when, how, where, why we use them. i am not clear on this concept. thanks in advance
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gudii9
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gudii9
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for_yanCommented:

This is from doc API:
http://download.oracle.com/javase/1.4.2/docs/api/java/util/Map.html

The Map interface provides three collection views, which allow a map's contents to be viewed as a set of keys, collection of values, or set of key-value mappings. The order of a map is defined as the order in which the iterators on the map's collection views return their elements. Some map implementations, like the TreeMap class, make specific guarantees as to their order; others, like the HashMap class, do not.
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gudii9Author Commented:
>>The Map interface provides three collection views

what is collection view. please elaborate on this. does any other collection objects like set, list etc has collection views?
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for_yanCommented:
They just explain that when considering the Map interface we
can think of te set of keys, collection of vlaues or babout set of Key-Value entries
It just comes form the nature of what is a Map as entity which maps one object to another and has a set of such pairs.
Once there is a set of these pairs - you may think about the set of keys, you may think about collection of values (values may be duplicates, so they are not set,
as we name by Set -a collection which does not have duplicates).

If you think about say ArrayList - you'll not have idea about such other collections whiach are so naturally related
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