Rethinking Levels as a doubly-indexed list

DoublyIndexedList.java

import java.util.ArrayList;
import java.util.List;

public class DoublyIndexedList {
    private Sprite[][] level;

    /* ... */

    public void set(int x, int y, Sprite sprite) {
        level[x][y] = sprite;
    }
    
    public Sprite get(int x, int y) {
        return level[x][y];
    }
    
    public List<Sprite> getColumn(int column) {
        List<Sprite> result = new ArrayList<>();
        for (Sprite s : level[column]) {
            if (s != null) {
                result.add(s);
            }
        }
        return result;
    }
    
    public List<Sprite> getRow(int row) {
        List<Sprite> result = new ArrayList<>();
        for (Sprite[] column : level) {
            if (column[row] != null) {
                result.add(column[row]);
            }
        }
        return result;
    }
}