I have a map which has as key string, and as a value a list of objects Names. In this map, I saved information some years about a Names. Each object of the `` class has a name, gender and rank atributes.
Map <String, ArrayList<Names>> myMap = new TreeMap<>();
I tried to do this but it doesn't work:
List<Names> filterList = myMap.filter((k, v) -> v.name == name).collect(Collectors.toList);
Assuming that the input map is like this:
Map<String, List<BabyName>> inputMap;
The list of BabyName should be retrieved using flatMap and filter operations of Stream API:
List<BabyName> result = inputMap.values() // Collection<List<BabyName>>
.stream() // Stream<List<BabyName>>
.flatMap(List::stream) // Stream<BabyName>
.filter(bn -> bn.getRank() == 3) // filtered Stream<BabyName>
.collect(Collectors.toList());
This is how I would have done it, not sure if I am being helpful here. I'm fairly new to Java and programming in general.
//Method that takes an ArrayList, filter the list, and returns a new ArrayList
public static ArrayList<BabyName> filterArrayList(ArrayList<BabyName> inputList, int filter) {
ArrayList<BabyName> returnList = new ArrayList<>();
for (BabyName babyName: inputList) {
if (babyName.getRank() == filter)
returnList.add(babyName);
} return returnList;
}
This block of code basically iterates the TreeMap, and calls the above method. The ArrayList returned by the above method gets added to a new ArrayList mFilteredList.
ArrayList<BabyName> mFilteredList = new ArrayList<>();
for (Iterator<ArrayList<BabyName>> iterator = myMap.values().iterator(); iterator.hasNext(); ) {
ArrayList<BabyName> nameList = iterator.next();
mFilteredList.addAll(filterArrayList(nameList, 2));
}
