// GcExcel 保存工作簿為CSV
Workbook workbook = new Workbook();

// 對workbook添加數據

workbook.save("SaveWorkbookToCsvFile.csv");


// POI 導出CSV
/**
\* A rudimentary XLSX -> CSV processor modeled on the
\* POI sample program XLS2CSVmra by Nick Burch from the
\* package org.apache.poi.hssf.eventusermodel.examples.
\* Unlike the HSSF version, this one completely ignores
\* missing rows.
\* 
\* Data sheets are read using a SAX parser to keep the
\* memory footprint relatively small, so this should be
\* able to read enormous workbooks.  The styles table and
\* the shared-string table must be kept in memory.  The
\* standard POI styles table class is used, but a custom
\* (read-only) class is used for the shared string table
\* because the standard POI SharedStringsTable grows very
\* quickly with the number of unique strings.
\* 
\* Thanks to Eric Smith for a patch that fixes a problem
\* triggered by cells with multiple "t" elements, which is
\* how Excel represents different formats (e.g., one word
\* plain and one word bold).
\*
\* @author Chris Lott
*/
public class ApacheXLSX2CSV {
 /**
  * The type of the data value is indicated by an attribute on the cell.
  * The value is usually in a "v" element within the cell.
  */
 enum xssfDataType {
     BOOL,
     ERROR,
     FORMULA,
     INLINESTR,
     SSTINDEX,
     NUMBER,
 }

 /**
  * Derived from http://poi.apache.org/spreadsheet/how-to.html#xssf_sax_api
  * 
  * Also see Standard ECMA-376, 1st edition, part 4, pages 1928ff, at
  * http://www.ecma-international.org/publications/standards/Ecma-376.htm
  * 
  * A web-friendly version is http://openiso.org/Ecma/376/Part4
  */
 class MyXSSFSheetHandler extends DefaultHandler {
     /**
      * Table with styles
      */
     private StylesTable stylesTable;
     /**
      * Table with unique strings
      */
     private ReadOnlySharedStringsTable sharedStringsTable;
     /**
      * Destination for data
      */
     private final PrintStream output;
     /**
      * Number of columns to read starting with leftmost
      */
     private final int minColumnCount;
     // Set when V start element is seen
     private boolean vIsOpen;
     // Set when cell start element is seen;
     // used when cell close element is seen.
     private xssfDataType nextDataType;
     // Used to format numeric cell values.
     private short formatIndex;
     private String formatString;
     private final DataFormatter formatter;
     private int thisColumn = -1;
     // The last column printed to the output stream
     private int lastColumnNumber = -1;
     // Gathers characters as they are seen.
     private StringBuffer value;
     /**
      * Accepts objects needed while parsing.
      *
      * @param styles  Table of styles
      * @param strings Table of shared strings
      * @param cols    Minimum number of columns to show
      * @param target  Sink for output
      */
     public MyXSSFSheetHandler(
             StylesTable styles,
             ReadOnlySharedStringsTable strings,
             int cols,
             PrintStream target) {
         this.stylesTable = styles;
         this.sharedStringsTable = strings;
         this.minColumnCount = cols;
         this.output = target;
         this.value = new StringBuffer();
         this.nextDataType = xssfDataType.NUMBER;
         this.formatter = new DataFormatter();
     }
     /*
        * (non-Javadoc)
        * @see org.xml.sax.helpers.DefaultHandler#startElement(java.lang.String, java.lang.String, java.lang.String, org.xml.sax.Attributes)
        */
     public void startElement(String uri, String localName, String name,
                              Attributes attributes) throws SAXException {
         if ("inlineStr".equals(name) || "v".equals(name)) {
             vIsOpen = true;
             // Clear contents cache
             value.setLength(0);
         }
         // c => cell
         else if ("c".equals(name)) {
             // Get the cell reference
             String r = attributes.getValue("r");
             int firstDigit = -1;
             for (int c = 0; c < r.length(); ++c) {
                 if (Character.isDigit(r.charAt(c))) {
                     firstDigit = c;
                     break;
                 }
             }
             thisColumn = nameToColumn(r.substring(0, firstDigit));
             // Set up defaults.
             this.nextDataType = xssfDataType.NUMBER;
             this.formatIndex = -1;
             this.formatString = null;
             String cellType = attributes.getValue("t");
             String cellStyleStr = attributes.getValue("s");
             if ("b".equals(cellType))
                 nextDataType = xssfDataType.BOOL;
             else if ("e".equals(cellType))
                 nextDataType = xssfDataType.ERROR;
             else if ("inlineStr".equals(cellType))
                 nextDataType = xssfDataType.INLINESTR;
             else if ("s".equals(cellType))
                 nextDataType = xssfDataType.SSTINDEX;
             else if ("str".equals(cellType))
                 nextDataType = xssfDataType.FORMULA;
             else if (cellStyleStr != null) {
                 // It's a number, but almost certainly one
                 //  with a special style or format
                 int styleIndex = Integer.parseInt(cellStyleStr);
                 XSSFCellStyle style = stylesTable.getStyleAt(styleIndex);
                 this.formatIndex = style.getDataFormat();
                 this.formatString = style.getDataFormatString();
                 if (this.formatString == null)
                     this.formatString = BuiltinFormats.getBuiltinFormat(this.formatIndex);
             }
         }
     }
     /*
        * (non-Javadoc)
        * @see org.xml.sax.helpers.DefaultHandler#endElement(java.lang.String, java.lang.String, java.lang.String)
        */
     public void endElement(String uri, String localName, String name)
             throws SAXException {
         String thisStr = null;
         // v => contents of a cell
         if ("v".equals(name)) {
             // Process the value contents as required.
             // Do now, as characters() may be called more than once
             switch (nextDataType) {
                 case BOOL:
                     char first = value.charAt(0);
                     thisStr = first == '0' ? "FALSE" : "TRUE";
                     break;
                 case ERROR:
                     thisStr = "\"ERROR:" + value.toString() + '"';
                     break;
                 case FORMULA:
                     // A formula could result in a string value,
                     // so always add double-quote characters.
                     thisStr = '"' + value.toString() + '"';
                     break;
                 case INLINESTR:
                     // TODO: have seen an example of this, so it's untested.
                     XSSFRichTextString rtsi = new XSSFRichTextString(value.toString());
                     thisStr = '"' + rtsi.toString() + '"';
                     break;
                 case SSTINDEX:
                     String sstIndex = value.toString();
                     try {
                         int idx = Integer.parseInt(sstIndex);
                         XSSFRichTextString rtss = new XSSFRichTextString(sharedStringsTable.getEntryAt(idx));
                         thisStr = '"' + rtss.toString() + '"';
                     }
                     catch (NumberFormatException ex) {
                         output.println("Failed to parse SST index '" + sstIndex + "': " + ex.toString());
                     }
                     break;
                 case NUMBER:
                     String n = value.toString();
                     if (this.formatString != null)
                         thisStr = formatter.formatRawCellContents(Double.parseDouble(n), this.formatIndex, this.formatString);
                     else
                         thisStr = n;
                     break;
                 default:
                     thisStr = "(TODO: Unexpected type: " + nextDataType + ")";
                     break;
             }
             // Output after we've seen the string contents
             // Emit commas for any fields that were missing on this row
             if (lastColumnNumber == -1) {
                 lastColumnNumber = 0;
             }
             for (int i = lastColumnNumber; i < thisColumn; ++i)
                 output.print(',');
             // Might be the empty string.
             output.print(thisStr);
             // Update column
             if (thisColumn > -1)
                 lastColumnNumber = thisColumn;
         } else if ("row".equals(name)) {
             // Print out any missing commas if needed
             if (minColumns > 0) {
                 // Columns are 0 based
                 if (lastColumnNumber == -1) {
                     lastColumnNumber = 0;
                 }
                 for (int i = lastColumnNumber; i < (this.minColumnCount); i++) {
                     output.print(',');
                 }
             }
             // We're onto a new row
             output.println();
             lastColumnNumber = -1;
         }
     }
     /**
      * Captures characters only if a suitable element is open.
      * Originally was just "v"; extended for inlineStr also.
      */
     public void characters(char[] ch, int start, int length)
             throws SAXException {
         if (vIsOpen)
             value.append(ch, start, length);
     }
     /**
      * Converts an Excel column name like "C" to a zero-based index.
      *
      * @param name
      * @return Index corresponding to the specified name
      */
     private int nameToColumn(String name) {
         int column = -1;
         for (int i = 0; i < name.length(); ++i) {
             int c = name.charAt(i);
             column = (column + 1) * 26 + c - 'A';
         }
         return column;
     }
 }
 ///////////////////////////////////////
 private OPCPackage xlsxPackage;
 private int minColumns;
 private PrintStream output;
 /**
  * Creates a new XLSX -> CSV converter
  *
  * @param pkg        The XLSX package to process
  * @param output     The PrintStream to output the CSV to
  * @param minColumns The minimum number of columns to output, or -1 for no minimum
  */
 public ApacheXLSX2CSV(OPCPackage pkg, PrintStream output, int minColumns) {
     this.xlsxPackage = pkg;
     this.output = output;
     this.minColumns = minColumns;
 }
 /**
  * Parses and shows the content of one sheet
  * using the specified styles and shared-strings tables.
  *
  * @param styles
  * @param strings
  * @param sheetInputStream
  */
 public void processSheet(
         StylesTable styles,
         ReadOnlySharedStringsTable strings,
         InputStream sheetInputStream)
         throws IOException, ParserConfigurationException, SAXException {
     InputSource sheetSource = new InputSource(sheetInputStream);
     SAXParserFactory saxFactory = SAXParserFactory.newInstance();
     SAXParser saxParser = saxFactory.newSAXParser();
     XMLReader sheetParser = saxParser.getXMLReader();
     ContentHandler handler = new MyXSSFSheetHandler(styles, strings, this.minColumns, this.output);
     sheetParser.setContentHandler(handler);
     sheetParser.parse(sheetSource);
 }
 /**
  * Initiates the processing of the XLS workbook file to CSV.
  *
  * @throws IOException
  * @throws OpenXML4JException
  * @throws ParserConfigurationException
  * @throws SAXException
  */
 public void process()
         throws IOException, OpenXML4JException, ParserConfigurationException, SAXException {
     ReadOnlySharedStringsTable strings = new ReadOnlySharedStringsTable(this.xlsxPackage);
     XSSFReader xssfReader = new XSSFReader(this.xlsxPackage);
     StylesTable styles = xssfReader.getStylesTable();
     XSSFReader.SheetIterator iter = (XSSFReader.SheetIterator) xssfReader.getSheetsData();
     int index = 0;
     while (iter.hasNext()) {
         InputStream stream = iter.next();
         String sheetName = iter.getSheetName();
         this.output.println();
         this.output.println(sheetName + " [index=" + index + "]:");
         processSheet(styles, strings, stream);
         stream.close();
         ++index;
     }
 }
 public static void main(String[] args) throws Exception
 {
     String dataPath = "src/featurescomparison/workingwithworksheets/converttocsv/data/";
     File xlsxFile = new File(dataPath + "workbook.xls");
     if (!xlsxFile.exists())
     {
         System.err.println("Not found or not a file: " + xlsxFile.getPath());
         return;
     }
     int minColumns = -1;
     if (args.length >= 2)
         minColumns = Integer.parseInt(args[1]);
     // The package open is instantaneous, as it should be.
     OPCPackage p = OPCPackage.open(xlsxFile.getPath(), PackageAccess.READ);
     ApacheXLSX2CSV xlsx2csv = new ApacheXLSX2CSV(p, System.out, minColumns);
     xlsx2csv.process();
}
    

                                    
//GcExcel 創建worksheet
Workbook wb = new Workbook();
wb.getWorksheets().add();
wb.save("TestOutput/GcExcel/Workbook.xlsx");

//POI 創建worksheet
Workbook wb = new XSSFWorkbook();
Sheet sheet1 = wb.createSheet("sheet1");
Sheet sheet2 = wb.createSheet("sheet2");
try (OutputStream fileOut = new FileOutputStream("TestOutput/Poi/Workbook.xlsx")) {
    wb.write(fileOut);
} catch (IOException e) {
    throw new RuntimeException(e);
}
    

                                    
//例如希望從Excel上獲取特定范圍的數據
//GcExcel
Workbook wb = new Workbook();
IWorksheet sheet1 = wb.getWorksheets().get(0);
Object[][] values = (Object[][]) sheet1.getRange("A1:Z26").getValue();

//Apache POI
Workbook wb = new XSSFWorkbook();
wb.createSheet();
for (Sheet sheet : wb) {
    for (Row row : sheet) {
        for (Cell cell : row) {
            //操作單元格獲取值
        }
    }
}