Unique values in my ArrayList

Question

I have next class:

private class LocoList{
    String Id;
    String Name;
    String Latitude;
    String Longitude;

    LocoList(String LocationId, String LocationName,  String 
        LocationLatitude, String LocationLongitude){

        this.Id = LocationId;
        this.Name = LocationName;
        this.Latitude = LocationLatitude;
        this.Longitude = LocationLongitude;
        }

    @Override public boolean equals(Object obj) {
        if (obj == this) { return true; }
        if (obj == null || obj.getClass() != this.getClass()) { return false; }
        NearLocoList guest = (NearLocoList) obj;
        return Id == guest.Id;
    }

    @Override
    public int hashCode() {
        return Objects.hash(Id);
    }

}

to use with next array:

private ArrayList<LocoList> myLocations = new ArrayList<>();

To populate my arrayList I use next method:

private void getLocoDatabase(LatLng PoI) {

    double mLatitude, mLongitude;
    mLatitude = PoI.latitude;
    mLongitude = PoI.longitude;

    ArrayList<ArrayList<Object>> dataLocation =
            mDBhelperMA.getLocations(mLatitude, mLongitude);

   for (int i = 0; i < dataLocation.size(); i++) {
        ArrayList<Object> row = dataLocation.get(i);

  if (!myLocations.contains(new LocoList(row.get(0).toString(), row.get(1).toString(), row.get(2).toString(),row.get(3).toString) {
        myLocations.add(new LocoList(row.get(0).toString(), row.get(1).toString(), row.get(2).toString(),row.get(3).toString);
        }
    }
}

My problem is that need to call GetLocoDatabase couple times for different LatLng and want to avoid duplicated values.

What I must to do to can have on myLocations ArrayList just unique values? Want to avoid to have same location twice or more.

Have tested but still get double values. I need to get uniques Id for LocoList on my List. — gogoloi, Dec 15 '17 at 10:42
Do not test equality of objects with ==, use `equals`. So change `Id == guest.Id` to `Id.equals(guest.Id)` (use a null check if it's possible for `Id` to be null). — nasch, Dec 16 '17 at 02:53

score 2 · Accepted Answer · answered Dec 15 '17 at 10:00

You have to do two things:

override the default equals()/hashCode() implementaiton
change from using a List/ArrayList to a Set/HashSet for example

You have to understand that different collection classes have different properties. When "uniqueness" is your primary concern, then use sets, not lists.

SKT · Answer 2 · 2017-12-15T11:28:56.280

0

Override equals method in LocoList and decide on what conditions two LocoList object will be be considered equal.

Then when adding the object to arraylist do a .contains check and add only if value does not exist

--Edit--

How to use equals

@Override 
public boolean equals(Object obj) {        
    if (obj != null) { 
        LocoList compareObj = (LocoList) obj;
        if (compareObj.id == id)
            return true;
    }
    return false;
}

How to use contains

LocoList myObj = new LocoList(row.get(0).toString(), row.get(1).toString(),
                      row.get(2).toString(), row.get(3).toString;
if (!myLocations.contains(myObj) {
    myLocations.add(myObj);
}

edited Dec 15 '17 at 11:28

answered Dec 15 '17 at 09:57

SKT

1,821
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Have tested and updated the question code. Stil get double values. – gogoloi Dec 15 '17 at 10:38
You told him to use == to test equality. He should be using `equals` instead. – nasch Dec 16 '17 at 02:54

score 0 · Answer 3 · answered Dec 15 '17 at 10:00

0

You can use set to strore the list

Set<String> set = new LinkedHashSet<>(list);

or

 Set<String> set = new LinkedHashSet<>;
set .addAll(list);
list.clear();
list.addAll(set )

;

answered Dec 15 '17 at 10:00

Kapil Parmar

881
8
19

Have tested already and get duplicates. Maybe because I use a class instead String. – gogoloi Dec 15 '17 at 10:26

Unique values in my ArrayList

3 Answers3