import java.util.ArrayList;
import java.util.Iterator;
import java.util.Objects;

public class SetArtilleriesGeneric<T> {
    private final ArrayList<T> _places;
    private final int _maxCount;

    public int getCount() {
        return _places.size();
    }

    public SetArtilleriesGeneric(int count) {
        _maxCount = count;
        _places = new ArrayList<>(count);
    }

    public int insert(T artillery) {
        return insert(artillery, 0);
    }

    public int insert(T artillery, int position) {
        if (position < 0 || position >= getCount() || getCount() == _maxCount) {
            return -1;
        }

        _places.add(position, artillery);

        return position;
    }

    public T remove(int position) {
        if (position < 0 || position >= getCount())
        {
            return null;
        }

        T result = _places.get(position);

        _places.remove(position);

        return result;
    }

    public T get(int position) {
        if (position < 0 || position >= getCount()) {
            return null;
        }

        return _places.get(position);
    }

    public Iterable<T> getArtilleries() {
        return () -> _places.stream().filter(Objects::nonNull).iterator();
    }
}