1 library(jpl): A Java interface for SWI Prolog 7.x
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[nondet]jpl_map_element(+Map:jref, -KeyValue:pair(datum,datum))
Map must be a JPL Reference to an object which implements the java.util.Map interface

This generates each Key-Value pair from the Map, e.g. 

?- jpl_call('java.lang.System', getProperties, [], Map), jpl_map_element(Map, E).
Map = @<jref>(0x20b5c38),
E = 'java.runtime.name'-'Java(TM) SE Runtime Environment' ;
Map = @<jref>(0x20b5c38),
E = 'sun.boot.library.path'-'C:\\Program Files\\Java\\jre7\\bin'
etc.

This is a utility predicate, defined thus: 

jpl_map_element(Map, K-V) :-
    jpl_call(Map, entrySet, [], ES),
    jpl_set_element(ES, E),
    jpl_call(E, getKey, [], K),
    jpl_call(E, getValue, [], V).
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