java - what is the reason behind the interface Map have inner interface Entry? -

i going through how java classes , interfaces designed , saw java/util/map.java , got below doubt ? please me answering.

what reason behind interface map have inner interface entry?
please see source code of java/util/map.java , answer.

map<k,v> can viewed associative storage (i.e. container connects keys values). can viewed collection of pairs, first element key, , second element corresponding value.

the majority of methods in map<k,v> supports associative container view of map. map.entry<k,v> interface there support other view of map - i.e. collection of key-value pairs.

each map provides access called entry set, set of pairs map. each pair represented instance of map.entry<k,v>.

map<integer,string> mymap = ... (map.entry<integer,string> e : mymap.entryset()) {     system.out.println(e.getkey()+" ---> "+e.getvalue()); } 

one have defined mapentry<k,v> interface outside map<k,v>. however, since interface closely related map, decision nest interface inside map makes perfect sense.