if (!getRowKeys().equals(that.getRowKeys())) {
            return false;
        }
        if (!getColumnKeys().equals(that.getColumnKeys())) {
            return false;
        }
        int rowCount = getRowCount();
        if (rowCount != that.getRowCount()) {
            return false;
        }
        int colCount = getColumnCount();
        if (colCount != that.getColumnCount()) {
            return false;
        }
        for (int r = 0; r < rowCount; r++) {
            for (int c = 0; c < colCount; c++) {
                Object v1 = getObject(r, c);
                Object v2 = that.getObject(r, c);
                if (v1 == null) {
                    if (v2 != null) {
                        return false;
                    }
                }
                else {
                    if (!v1.equals(v2)) {
                        return false;
                    }
                }
            }
        }
        return true;