Map Utils

• Merge Maps

public static List> mergeMaps
(List> list1, List> list2, String primKey) {

List> output = new ArrayList>(list1.size());
Object key1, key2;
Map map;
for(Map map1:list1){

key1 = map1.get(primKey);
map = new HashMap();
map.putAll(map1);
for(Map map2:list2){
key2 = map2.get(primKey);
if(key1.equals(key2)){
map.putAll(map2);
break;
}
}
output.add(map);
}
return output;
}

• Normalize Map

/**
* If the input list is like this:
* [
* {ID=3, TAG=Tag1, NAME=Name1},
* {ID=3, TAG=Tag2, NAME=Name1},
* {ID=3, TAG=Tag3, NAME=Name1},
* {ID=4, TAG=Tag4, NAME=Name2},
* {ID=4, TAG=Tag5, NAME=Name2},
* {ID=5, TAG=Tag6, NAME=Name3}
* ]
*
* The output list would look like this:
* [
* {ID=3, TAG=[Tag1, Tag2, Tag3], NAME=Name1},
* {ID=4, TAG=[Tag4, Tag5], NAME=Name2},
* {ID=5, TAG=[Tag6], NAME=Name3}
* ]
*
* @param list
* @param primKey (E.g.: ID)
* @param joinKey (E.g.: TAG)
* @param stripOtherCols - dictates if other fields in the map (like: NAME) needs to be stripped or preserved in output.
* @return
*/
@SuppressWarnings("unchecked")
public static List> normalize
(List> list, String primKey, String joinKey, boolean stripOtherCols) {

Map> outputMap = new HashMap>();
Map innerOutputMap;

for(Map innerInputMap:list){
if( (innerOutputMap = outputMap.get( innerInputMap.get(primKey).toString() ) ) == null ){
innerOutputMap = populateInnerOutputmap(innerInputMap, primKey, joinKey, stripOtherCols);
outputMap.put(innerInputMap.get(primKey).toString(),innerOutputMap);
}
if( isNotNull(innerInputMap.get(joinKey)) ){
List itemList = (List)innerOutputMap.get(joinKey);
itemList.add( innerInputMap.get(joinKey) );
}
}
List> outputList =
(List)Arrays.asList( outputMap.values().toArray() );

return outputList;
}

• De-normalize Key Value Pair

/**
* If the input list is like this:
* [
* {VAL=Val1, ID=3, KEY=Key1, NAME=Name1},
* {VAL=Val2, ID=3, KEY=Key2, NAME=Name1},
* {VAL=Val3, ID=3, KEY=Key3, NAME=Name1},
* {VAL=Val4, ID=4, KEY=Key4, NAME=Name1},
* {VAL=Val5, ID=4, KEY=Key5, NAME=Name1},
* {VAL=Val6, ID=5, KEY=Key6, NAME=Name1}
* ]
*
* The output list would look like this:
* [
* {ID=3, Key1=Val1, Key3=Val3, Key2=Val2, NAME=Name1},
* {ID=5, Key6=Val6, NAME=Name1},
* {ID=4, Key4=Val4, Key5=Val5, NAME=Name1}
* ]
*
* @param list
* @param primKey
* @param key
* @param val
* @param stripOtherCols - dictates if other fields in the map (like: NAME) needs to be stripped or preserved in output.
* @return
*/
@SuppressWarnings("unchecked")
public static List> denormalizeKeyValuePair
(List> list, String primKey, String key, String val, boolean stripOtherCols) {

Map> outputMap = new HashMap>();
Map innerOutputMap;

for(Map innerInputMap:list){
if( (innerOutputMap = outputMap.get( innerInputMap.get(primKey).toString() )) == null){
innerOutputMap = populateInnerOutputmap(innerInputMap, primKey, null, stripOtherCols);
outputMap.put(innerInputMap.get(primKey).toString(),innerOutputMap);
}
if( isNotNull(innerInputMap.get(key)) && isNotNull(innerInputMap.get(val))){
innerOutputMap.put((String)innerInputMap.get(key), innerInputMap.get(val));
}
}

List> outputList =
(List)Arrays.asList( outputMap.values().toArray() );

return outputList;
}

• Populate InnerOutputmap

private static Map populateInnerOutputmap
(Map innerInputMap, String primKey, String joinKey, boolean stripOtherCols){

Map innerOutputMap = new HashMap();
if( stripOtherCols ){
innerOutputMap.put(primKey, innerInputMap.get(primKey));
}else{
innerOutputMap.putAll(innerInputMap);
}
if(joinKey != null ){
innerOutputMap.put(joinKey, new ArrayList());
}
return innerOutputMap;
}

• isNotNull

private static boolean isNotNull(Object obj){
if(obj != null ){
//This special check for String is because of Oracle (probably all DBs have similar behavior)
//Null values are sent as String 'null'. Probably we can use something like NVL to avoind that.
//Once NVL stuff is tested, we can remove this 'null' check
if( obj instanceof String) {
if( !"null".equalsIgnoreCase( (String)obj ) & ((String)obj).length() > 0 ){
return true;
}else{
return false;
}
}else{
return true;
}
}else{
return false;
}
}