public class Grid {

  // Create a window showing an all-white empty grid with the
  // given number of rows and columns.
  // Individual squares are addressed with a row number in range 0 to rowCount-1
  // and a column number in range 0 to columnCount-1.
  public static void create (int rowCount, int columnCount);

  // Place an item on the given square, replacing any existing item.
  // Uses the default color Grid.BLACK for the new item.

public static void placeItem (int row, int column, char item);

  // Place an item on the given square, replacing any existing item.
  // Uses the specified color Grid.… for the new item.

public static void placeItem (int row, int column, char item, Color itemColor);

  // Removes any item from the given square.
  // Silently does nothing, if there is no item on that square.

public static void removeItem (int row, int column);

  // Paint the background of the given square with specified color Grid.….
  // The previous background color is completely replaced with the new color.

public static void paintFloor (int row, int column, Color floorColor);

  // A shortcut method to clear the background color of the given square to
  // the original color Grid.WHITE.

public static void clearFloor (int row, int column);

  // Named constants for all predefined colors
  public static final Color BLACK = …;
  public static final Color WHITE = …;
  public static final Color GRAY = …;
  public static final Color RED = …;
  public static final Color GREEN = …;
  public static final Color BLUE = …;
  public static final Color YELLOW = …;
  public static final Color ORANGE = …;
  public static final Color CYAN = …;
  public static final Color VIOLET = …;
  public static final Color BROWN = …;

  // Predicate that tests whether the given row and column number refer to
  // a valid square inside the grid:
  // 0 <= row < rowCount  AND  0 <= column < columnCount.
  // All other Grid methods abort the program with an error message,
  // if row or column numbers beyond the bounds of the grid are used.

public static boolean insideBounds (int row, int column);
}