Question

1 hospital will have multiple doctors. and i need to know a java collection type(ArrayList,HashMap etc) where i could store hospital ID and a Doctor object in a suitable java collection type (ArrayList,HashMap etc).

The requirement is that i should be able to store the HospitalID as a key and the Doctor object as it’s value.

Furthermore, I should be able to have the same key for various Doctor object (as there can be many doctors working for the said hospital). So what is the java collection type (ArrayList,HashMap etc) where i can use for this scenario ?

Note: i can’t use a HashMap – because it takes unique IDs.

Later on i should be able to filter out all the doctors that work for a particular hospital (by searching from it’s ID) , and display its records

Answer 1

You can have an ArrayList of Doctor objects and then create a HashMap that stores the HospitalID as the key and ArrayList of doctors as the value:

ArrayList<Doctor> a = new ArrayList<Doctor>();
a.add(new Doctor());
// put all the doctors

HashMap<Integer,ArrayList<Doctor>> hMap = new HashMap<Integer,ArrayList<Doctor>>();
Integer hospitalId = new Intger(1);

hMap.put(hospitalId,a);

UPDATE:

For adding new doctor :

//Take the existing list from the map using hospitalId
ArrayList<Doctor> existingList = hMap.get(hospitalId);

Doctor d = new Doctor();
// add new doctor to existingList
existingList.add(d);

//put the new list again in the map

hMap.put(hospitalId,existingList);