Apache POI之Excel文档操作简单说明
最近小学妹遇到问题了，java里面Excel怎么操作啊?
作为学妹眼中“大神”的存在（其实是个菜瓜），虽然没吃过猪肉、家穷，也不能告诉她不会啊，马上打开http://poi.apache.org/spreadsheet/index.html ，学习一通。
在poi里面excel的操作被分为两种，一种专门处理xls结尾的表格叫HSSF，另一种专门处理xlsx结尾的表格叫XSSF。
这两个玩意儿都提供了三个层次的api方便处理excel：低级模式、效率模式、用户模式。
低级模式和用户模式都可以修改、生成excel，用户模式的问题是内存占用很高，但是真心简单。
效率模式是只读的，如果你仅仅是想读取excel里面的数据，建议用这个。
HSSF相比于XSSF来讲，内存占用要低，原因是前者是读的二进制的东东，后者基于xml的。
简答的创建excel的例子，无耻的copy自官网：
1.创建文件：
Workbook wb = new HSSFWorkbook();
FileOutputStream fileOut = new FileOutputStream("workbook.xls");
wb.write(fileOut);
fileOut.close();
Workbook wb = new XSSFWorkbook();
FileOutputStream fileOut = new FileOutputStream("workbook.xlsx");
wb.write(fileOut);
fileOut.close();
2.创建sheet
Workbook wb = new HSSFWorkbook(); // or new XSSFWorkbook();
Sheet sheet1 = wb.createSheet("new sheet");
Sheet sheet2 = wb.createSheet("second sheet");
// Note that sheet name is Excel must not exceed 31 characters
// and must not contain any of the any of the following characters:
// 0x0000
// 0x0003
// colon (:)
// backslash (\)
// asterisk (*)
// question mark (?)
// forward slash (/)
// opening square bracket ([)
// closing square bracket (])
// You can use org.apache.poi.ss.util.WorkbookUtil#createSafeSheetName(String nameProposal)}
// for a safe way to create valid names, this utility replaces invalid characters with a space (' ')
String safeName = WorkbookUtil.createSafeSheetName("[O'Brien's sales*?]"); // returns " O'Brien's sales "
Sheet sheet3 = wb.createSheet(safeName);
FileOutputStream fileOut = new FileOutputStream("workbook.xls");
wb.write(fileOut);
fileOut.close();
3.创建单元格
Workbook wb = new HSSFWorkbook();
//Workbook wb = new XSSFWorkbook();
CreationHelper createHelper = wb.getCreationHelper();
Sheet sheet = wb.createSheet("new sheet");
// Create a row and put some cells in it. Rows are 0 based.
Row row = sheet.createRow((short) 0);
// Create a cell and put a value in it.
Cell cell = row.createCell(0);
cell.setCellValue(1);
// Or do it on one line.
row.createCell(1).setCellValue(1.2);
row.createCell(2).setCellValue(
createHelper.createRichTextString("This is a string"));
row.createCell(3).setCellValue(true);
// Write the output to a file
FileOutputStream fileOut = new FileOutputStream("workbook.xls");
wb.write(fileOut);
fileOut.close();
4.创建日期类型的单元格
Workbook wb = new HSSFWorkbook();
//Workbook wb = new XSSFWorkbook();
CreationHelper createHelper = wb.getCreationHelper();
Sheet sheet = wb.createSheet("new sheet");
// Create a row and put some cells in it. Rows are 0 based.
Row row = sheet.createRow(0);
// Create a cell and put a date value in it. The first cell is not styled
// as a date.
Cell cell = row.createCell(0);
cell.setCellValue(new Date());
// we style the second cell as a date (and time). It is important to
// create a new cell style from the workbook otherwise you can end up
// modifying the built in style and effecting not only this cell but other cells.
CellStyle cellStyle = wb.createCellStyle();
cellStyle.setDataFormat(
createHelper.createDataFormat().getFormat("m/d/yy h:mm"));
cell = row.createCell(1);
cell.setCellValue(new Date());
cell.setCellStyle(cellStyle);
//you can also set date as java.util.Calendar
cell = row.createCell(2);
cell.setCellValue(Calendar.getInstance());
cell.setCellStyle(cellStyle);
// Write the output to a file
FileOutputStream fileOut = new FileOutputStream("workbook.xls");
wb.write(fileOut);
fileOut.close();
5.使用不同类型的单元格
Workbook wb = new HSSFWorkbook();
Sheet sheet = wb.createSheet("new sheet");
Row row = sheet.createRow((short)2);
row.createCell(0).setCellValue(1.1);
row.createCell(1).setCellValue(new Date());
row.createCell(2).setCellValue(Calendar.getInstance());
row.createCell(3).setCellValue("a string");
row.createCell(4).setCellValue(true);
row.createCell(5).setCellType(Cell.CELL_TYPE_ERROR);
// Write the output to a file
FileOutputStream fileOut = new FileOutputStream("workbook.xls");
wb.write(fileOut);
fileOut.close();
使用poi创建excel真是简单啊,感觉并没有什么可以说的，这回以我的智商我又能秀起来了。
直接把这个地址发给学妹，搞定，手工。
http://poi.apache.org/spreadsheet/quick-guide.html