paintFill

    public static void paintFill(int[][] image, int x, int y, int oldColor, int newColor) {

        if (x < 0 || x == image[0].length || y < 0 || y == image.length) {
            return;
        }

        if (image[y][x] == oldColor) {
            image[y][x] = newColor;
            paintFill(image, x + 1, y, oldColor, newColor);
            paintFill(image, x - 1, y, oldColor, newColor);
            paintFill(image, x, y + 1, oldColor, newColor);
            paintFill(image, x, y - 1, oldColor, newColor);
        }
        return;
    }