private String cleanFormatForNumber(String formatStr) {
        StringBuilder sb = new StringBuilder(formatStr);

        if (emulateCSV) {
            // Requested spacers with "_" are replaced by a single space.
            // Full-column-width padding "*" are removed.
            // Not processing fractions at this time. Replace ? with space.
            // This matches CSV output.
            for (int i = 0; i < sb.length(); i++) {
                char c = sb.charAt(i);
                if (c == '_' || c == '*' || c == '?') {
                    if (i > 0 && sb.charAt((i - 1)) == '\\') {
                        // It's escaped, don't worry
                        continue;
                    }
                    if (c == '?') {
                        sb.setCharAt(i, ' ');
                    } else if (i < sb.length() - 1) {
                        // Remove the character we're supposed
                        // to match the space of / pad to the
                        // column width with
                        if (c == '_') {
                            sb.setCharAt(i + 1, ' ');
                        } else {
                            sb.deleteCharAt(i + 1);
                        }
                        // Remove the character too
                        sb.deleteCharAt(i);
                        i--;
                    }
                }
            }
        } else {
            // If they requested spacers, with "_",
            // remove those as we don't do spacing
            // If they requested full-column-width
            // padding, with "*", remove those too
            for (int i = 0; i < sb.length(); i++) {
                char c = sb.charAt(i);
                if (c == '_' || c == '*') {
                    if (i > 0 && sb.charAt((i - 1)) == '\\') {
                        // It's escaped, don't worry
                        continue;
                    }
                    if (i < sb.length() - 1) {
                        // Remove the character we're supposed
                        // to match the space of / pad to the
                        // column width with
                        sb.deleteCharAt(i + 1);
                    }
                    // Remove the _ too
                    sb.deleteCharAt(i);
                    i--;
                }
            }
        }

        // Now, handle the other aspects like
        // quoting and scientific notation
        for (int i = 0; i < sb.length(); i++) {
            char c = sb.charAt(i);
            // remove quotes and back slashes
            if (c == '\\' || c == '"') {
                sb.deleteCharAt(i);
                i--;

                // for scientific/engineering notation
            } else if (c == '+' && i > 0 && sb.charAt(i - 1) == 'E') {
                sb.deleteCharAt(i);
                i--;
            }
        }

        return sb.toString();
    }
Create and return a Format based on the format string from a cell's style. If the pattern cannot be parsed,
return a default pattern.

@param cell The Excel cell
@return A Format representing the excel format. May return null.
fastexcel-test/src/test/java/cn/idev/excel/test/temp/dataformat/DataFormatter1.java