Question

I am filtering the all list which ahve same lat,long in one list and put into an same list and put that list into map My code is as:-

private Collection<List<Applicationdataset>> groupTheList(ArrayList<Applicationdataset> arrayList)
  {
    Map<Key, List<Applicationdataset>> map = new HashMap<Key, List<Applicationdataset>>();
    for(Applicationdataset appSet: arrayList)
       {
        Key key = new Key(appSet.getLatitude(), appSet.getLongitude());
        List<Applicationdataset> list = map.get(key);
        if(list == null){
            list = new ArrayList<Applicationdataset>();

        }
        list.add(appSet);
             map.put(key, list);
    }
    return map.values();
}


public class Key {
    String _lat;
    String _lon;

    Key(String lat, String lon) {
        _lat = lat;
        _lon = lon;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        Key key = (Key) o;

        if (!_lat.equals(key._lat)) return false;
        if (!_lon.equals(key._lon)) return false;

        return true;
    }

    @Override
    public int hashCode() {
        int result = _lat.hashCode();
        result = 31 * result + _lon.hashCode();
        return result;
    }
}

But When I am debuging my code according to xml which come from web-service there is 2 list which have same lat long and they are saving in same list in amp at time of debuging but when I go next step of debug the element of map which have 2 item list decrease and showing size 1 I am unable to rectify this issue.

Answer 1

Your code looks OK: You’ve overridden equals() and hashCode() consistently.

Check for whitespace in the lat/lng values as the cause of your problems, perhaps trim() in the constructor:

Key(String lat, String lon) {
    _lat = lat.trim();
    _lon = lon.trim();
}

Also, you can simplify your code to this:

@Override
public boolean equals(Object o) {
    return o instanceof Key
        && _lat.equals(((Key)o)._lat))
        && _lon.equals(((Key)o)._lon));
}

@Override
public int hashCode() {
    // String.hashCode() is sufficiently good for this addition to be acceptable
    return _lat.hashCode() + _lon.hashCode();
}