example demonstrating how to generate large workbooks and avoid OutOfMemory exception
git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@724135 13f79535-47bb-0310-9956-ffa450edef68
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Yegor Kozlov
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/* ====================================================================
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Licensed to the Apache Software Foundation (ASF) under one or more
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contributor license agreements. See the NOTICE file distributed with
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this work for additional information regarding copyright ownership.
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The ASF licenses this file to You under the Apache License, Version 2.0
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(the "License"); you may not use this file except in compliance with
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the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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==================================================================== */
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package org.apache.poi.xssf.usermodel.examples;
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import org.apache.poi.xssf.usermodel.*;
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import org.apache.poi.ss.util.CellReference;
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import org.apache.poi.ss.usermodel.IndexedColors;
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import org.apache.poi.ss.usermodel.DateUtil;
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import java.io.*;
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import java.util.zip.ZipFile;
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import java.util.zip.ZipEntry;
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import java.util.zip.ZipOutputStream;
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import java.util.*;
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/**
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* Demonstrates a workaround you can use to generate large workbooks and avoid OutOfMemory exception.
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*
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* The trick is as follows:
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* 1. create a template workbook, create sheets and global objects such as cell styles, number formats, etc.
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* 2. create an application that streams data in a text file
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* 3. Substitute the sheet in the template with the generated data
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*
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* @author Yegor Kozlov
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*/
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public class BigGridDemo {
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public static void main(String[] args) throws Exception {
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// Step 1. Create a template file. Setup sheets and workbook-level objects such as
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// cell styles, number formats, etc.
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XSSFWorkbook wb = new XSSFWorkbook();
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XSSFSheet sheet = wb.createSheet("Big Grid");
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Map<String, XSSFCellStyle> styles = createStyles(wb);
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//name of the zip entry holding sheet data, e.g. /xl/worksheets/sheet1.xml
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String sheetRef = sheet.getPackagePart().getPartName().getName();
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//save the template
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FileOutputStream os = new FileOutputStream("template.xlsx");
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wb.write(os);
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os.close();
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//Step 2. Generate XML file.
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File tmp = File.createTempFile("sheet", ".xml");
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Writer fw = new FileWriter(tmp);
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generate(fw, styles);
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fw.close();
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//Step 3. Substitute the template entry with the generated data
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FileOutputStream out = new FileOutputStream("big-grid.xlsx");
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substitute(new File("template.xlsx"), tmp, sheetRef.substring(1), out);
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out.close();
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}
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/**
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* Create a library of cell styles.
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*/
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private static Map<String, XSSFCellStyle> createStyles(XSSFWorkbook wb){
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Map<String, XSSFCellStyle> styles = new HashMap<String, XSSFCellStyle>();
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XSSFDataFormat fmt = wb.createDataFormat();
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XSSFCellStyle style1 = wb.createCellStyle();
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style1.setAlignment(XSSFCellStyle.ALIGN_RIGHT);
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style1.setDataFormat(fmt.getFormat("0.0%"));
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styles.put("percent", style1);
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XSSFCellStyle style2 = wb.createCellStyle();
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style2.setAlignment(XSSFCellStyle.ALIGN_CENTER);
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style2.setDataFormat(fmt.getFormat("0.0X"));
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styles.put("coeff", style2);
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XSSFCellStyle style3 = wb.createCellStyle();
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style3.setAlignment(XSSFCellStyle.ALIGN_RIGHT);
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style3.setDataFormat(fmt.getFormat("$#,##0.00"));
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styles.put("currency", style3);
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XSSFCellStyle style4 = wb.createCellStyle();
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style4.setAlignment(XSSFCellStyle.ALIGN_RIGHT);
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style4.setDataFormat(fmt.getFormat("mmm dd"));
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styles.put("date", style4);
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XSSFCellStyle style5 = wb.createCellStyle();
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XSSFFont headerFont = wb.createFont();
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headerFont.setBold(true);
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style5.setFillForegroundColor(IndexedColors.GREY_25_PERCENT.getIndex());
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style5.setFillPattern(XSSFCellStyle.SOLID_FOREGROUND);
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style5.setFont(headerFont);
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styles.put("header", style5);
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return styles;
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}
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private static void generate(Writer out, Map<String, XSSFCellStyle> styles) throws Exception {
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Random rnd = new Random();
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Calendar calendar = Calendar.getInstance();
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SpreadsheetWriter sw = new SpreadsheetWriter(out);
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sw.beginSheet();
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//insert header row
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sw.insertRow(0);
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int styleIndex = styles.get("header").getIndex();
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sw.createCell(0, "Title", styleIndex);
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sw.createCell(1, "% Change", styleIndex);
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sw.createCell(2, "Ratio", styleIndex);
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sw.createCell(3, "Expenses", styleIndex);
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sw.createCell(4, "Date", styleIndex);
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sw.endRow();
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//write data rows
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for (int rownum = 1; rownum < 100000; rownum++) {
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sw.insertRow(rownum);
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sw.createCell(0, "Hello, " + rownum + "!");
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sw.createCell(1, (double)rnd.nextInt(100)/100, styles.get("percent").getIndex());
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sw.createCell(2, (double)rnd.nextInt(10)/10, styles.get("coeff").getIndex());
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sw.createCell(3, rnd.nextInt(10000), styles.get("currency").getIndex());
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sw.createCell(4, calendar, styles.get("date").getIndex());
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sw.endRow();
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calendar.roll(Calendar.DAY_OF_YEAR, 1);
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}
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sw.endSheet();
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}
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/**
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*
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* @param zipfile the template file
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* @param tmpfile the XML file with the sheet data
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* @param entry the name of the sheet entry to substitute, e.g. xl/worksheets/sheet1.xml
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* @param out the stream to write the result to
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*/
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private static void substitute(File zipfile, File tmpfile, String entry, OutputStream out) throws IOException {
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ZipFile zip = new ZipFile(zipfile);
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ZipOutputStream zos = new ZipOutputStream(out);
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for (Enumeration en = zip.entries(); en.hasMoreElements(); ) {
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ZipEntry ze = (ZipEntry)en.nextElement();
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if(!ze.getName().equals(entry)){
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zos.putNextEntry(new ZipEntry(ze.getName()));
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InputStream is = zip.getInputStream(ze);
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copyStream(is, zos);
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is.close();
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}
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}
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zos.putNextEntry(new ZipEntry(entry));
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InputStream is = new FileInputStream(tmpfile);
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copyStream(is, zos);
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is.close();
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zos.close();
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}
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private static void copyStream(InputStream in, OutputStream out) throws IOException {
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byte[] chunk = new byte[1024];
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int count;
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while ((count = in.read(chunk)) >=0 ) {
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out.write(chunk,0,count);
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}
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}
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/**
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* Writes spreadsheet data in a Writer.
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* (YK: in future it may evolve in a full-featured API for streaming data in Excel)
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*/
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public static class SpreadsheetWriter {
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private Writer out;
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private int rownum;
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public SpreadsheetWriter(Writer out){
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this.out = out;
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}
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public void beginSheet() throws IOException {
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out.write("<?xml version=\"1.0\" encoding=\"UTF-8\"?>" +
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"<worksheet xmlns=\"http://schemas.openxmlformats.org/spreadsheetml/2006/main\">" );
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out.write("<sheetData>\n");
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}
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public void endSheet() throws IOException {
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out.write("</sheetData>");
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out.write("</worksheet>");
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}
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/**
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* Insert a new row
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*
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* @param rownum 0-based row number
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*/
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public void insertRow(int rownum) throws IOException {
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out.write("<row r=\""+(rownum+1)+"\">\n");
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this.rownum = rownum;
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}
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/**
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* Insert row end marker
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*/
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public void endRow() throws IOException {
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out.write("</row>\n");
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}
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public void createCell(int columnIndex, String value, int styleIndex) throws IOException {
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String ref = new CellReference(rownum, columnIndex).formatAsString();
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out.write("<c r=\""+ref+"\" t=\"inlineStr\"");
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if(styleIndex != -1) out.write(" s=\""+styleIndex+"\"");
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out.write(">");
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out.write("<is><t>"+value+"</t></is>");
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out.write("</c>");
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}
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public void createCell(int columnIndex, String value) throws IOException {
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createCell(columnIndex, value, -1);
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}
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public void createCell(int columnIndex, double value, int styleIndex) throws IOException {
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String ref = new CellReference(rownum, columnIndex).formatAsString();
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out.write("<c r=\""+ref+"\" t=\"n\"");
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if(styleIndex != -1) out.write(" s=\""+styleIndex+"\"");
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out.write(">");
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out.write("<v>"+value+"</v>");
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out.write("</c>");
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}
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public void createCell(int columnIndex, double value) throws IOException {
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createCell(columnIndex, value, -1);
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}
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public void createCell(int columnIndex, Calendar value, int styleIndex) throws IOException {
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createCell(columnIndex, DateUtil.getExcelDate(value, false), styleIndex);
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}
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}
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}
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