Fastest Way To Find String In Map?

Question

problem: basically im trying to match the value of one Map with the key of another. my thinking is that this requires me to loop through the first Map and for each value through the second Map and match up the key to it. heres my code so far:
private static Map equiJoin(Map relation1, Map relation2) // The 2 maps
Map resultRelation = new TreeMap();
Iterator keys1Iterator = relation1.keySet().iterator();
Iterator values1Iterator = relation1.values().iterator();
while (keys1Iterator.hasNext() ) // Loop through relation1
String primaryKey1 = (String) keys1Iterator.next();
String foreignKey1 = (String) values1Iterator.next();
List list = new ArrayList();
Iterator keys2Iterator = relation2.keySet().iterator();
Iterator values2Iterator = relation2.values().iterator();
while (keys2Iterator.hasNext() ) // Loop through relation2
String primaryKey2 = (String) keys2Iterator.next();
String foreignKey2 = (String) values2Iterator.next();
if(primaryKey2.equals(foreignKey1))
list.add(foreignKey1);
list.add(foreignKey2);
resultRelation.put(primaryKey1, list);
return resultRelation;
im trying to come up with ways to make this faster, perhaps by turing the second while loop/linear search into a binary search.
any thoughts would be appreciated.

Answer 1

problem: basically im trying to match the value of one
Map with the key of another. my thinking is that this
requires me to loop through the first Map and for each
value through the second Map and match up the key to
it. heres my code so far:
private static Map equiJoin(Map relation1, Map
relation2) // The 2 maps
Map resultRelation = new TreeMap();
Iterator keys1Iterator =
relation1.keySet().iterator();
Iterator values1Iterator =
relation1.values().iterator();
while (keys1Iterator.hasNext() ) // Loop through
relation1
String primaryKey1 = (String) keys1Iterator.next();
String foreignKey1 = (String) values1Iterator.next();
List list = new ArrayList();
Iterator keys2Iterator =
relation2.keySet().iterator();
Iterator values2Iterator =
relation2.values().iterator();
while (keys2Iterator.hasNext() ) // Loop through
relation2
String primaryKey2 = (String) keys2Iterator.next();
String foreignKey2 = (String) values2Iterator.next();
if(primaryKey2.equals(foreignKey1))
list.add(foreignKey1);
list.add(foreignKey2);
resultRelation.put(primaryKey1, list);
return resultRelation;
im trying to come up with ways to make this faster,
perhaps by turing the second while loop/linear search
into a binary search.
any thoughts would be appreciated.Yep. The inner loop is not needed. Just use Map api.
Object value2 = relation2.get(primaryKey1);
// and check for null for value2, if null don't add to the list, if not null, do a resultRelation.put
btw, you list add logic:
if(primaryKey2.equals(foreignKey1))
list.add(foreignKey1);
list.add(foreignKey2);
resultRelation.put(primaryKey1, list);
} why do you add both foreignKey1 and foreignKey2 to the list when they are equals. Since they are equals, are they redundent?
--lichu