public class OxygenFiller
{
    public OxygenFiller (Maze theMaze)
    {
        _theMaze = theMaze;
    }

    public int fillWithOxygen ()
    {
        int steps = 0;

        return steps;
    }

    private Maze _theMaze;
}
public class OxygenFiller
{
    public OxygenFiller (Maze theMaze)
    {
        _theMaze = theMaze;
    }

    // trace through the maze until we get back to the start
    
    public int fillWithOxygen ()
    {
        int steps = 0;

        return steps;
    }

    private Maze _theMaze;
}
Update OxygenFiller.java