POI官方网址：http://poi.apache.org/
POI的功能实在很强大，而且是apache的子项目，它下面又包含一些Component，比如处理Excel XLS，PowerPoint PPT，Word DOC，Outlook MSG，Excel XLSX等，下面就简单讲下poi处理excel的一些内容。

下面的jar包来源于当前最新的poi 3.6版本。

1.poi来生成excel

package com.test.poi;

import java.io.FileOutputStream;
import java.util.Date;

import org.apache.poi.hssf.usermodel.HSSFCell;
import org.apache.poi.hssf.usermodel.HSSFCellStyle;
import org.apache.poi.hssf.usermodel.HSSFDataFormat;
import org.apache.poi.hssf.usermodel.HSSFFont;
import org.apache.poi.hssf.usermodel.HSSFHyperlink;
import org.apache.poi.hssf.usermodel.HSSFRow;
import org.apache.poi.hssf.usermodel.HSSFSheet;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.hssf.util.HSSFColor;
import org.apache.poi.ss.util.CellRangeAddress;

public class WriteExcel {

public static void main(String[] args) throws Exception {
    // 创建Excel的工作书册 Workbook,对应到一个excel文档
    HSSFWorkbook wb = new HSSFWorkbook();

// 创建Excel的工作sheet,对应到一个excel文档的tab
    HSSFSheet sheet = wb.createSheet("sheet1");

// 设置excel每列宽度
    sheet.setColumnWidth(0, 4000);
    sheet.setColumnWidth(1, 3500);

// 创建字体样式
    HSSFFont font = wb.createFont();
    font.setFontName("Verdana");
    font.setBoldweight((short) 100);
    font.setFontHeight((short) 300);
    font.setColor(HSSFColor.BLUE.index);

// 创建单元格样式
    HSSFCellStyle style = wb.createCellStyle();
    style.setAlignment(HSSFCellStyle.ALIGN_CENTER);
    style.setVerticalAlignment(HSSFCellStyle.VERTICAL_CENTER);
    style.setFillForegroundColor(HSSFColor.LIGHT_TURQUOISE.index);
    style.setFillPattern(HSSFCellStyle.SOLID_FOREGROUND);

// 设置边框
    style.setBottomBorderColor(HSSFColor.RED.index);
    style.setBorderBottom(HSSFCellStyle.BORDER_THIN);
    style.setBorderLeft(HSSFCellStyle.BORDER_THIN);
    style.setBorderRight(HSSFCellStyle.BORDER_THIN);
    style.setBorderTop(HSSFCellStyle.BORDER_THIN);

style.setFont(font);// 设置字体

// 创建Excel的sheet的一行
    HSSFRow row = sheet.createRow(0);
    row.setHeight((short) 500);// 设定行的高度
    // 创建一个Excel的单元格
    HSSFCell cell = row.createCell(0);

// 合并单元格(startRow，endRow，startColumn，endColumn)
    sheet.addMergedRegion(new CellRangeAddress(0, 0, 0, 2));

// 给Excel的单元格设置样式和赋值
    cell.setCellStyle(style);
    cell.setCellValue("hello world");

// 设置单元格内容格式
    HSSFCellStyle style1 = wb.createCellStyle();
    style1.setDataFormat(HSSFDataFormat.getBuiltinFormat("h:mm:ss"));

style1.setWrapText(true);// 自动换行

row = sheet.createRow(1);

// 设置单元格的样式格式

cell = row.createCell(0);
    cell.setCellStyle(style1);
    cell.setCellValue(new Date());

// 创建超链接
    HSSFHyperlink link = new HSSFHyperlink(HSSFHyperlink.LINK_URL);
    link.setAddress("http://www.baidu.com");
    cell = row.createCell(1);
    cell.setCellValue("百度");
    cell.setHyperlink(link);// 设定单元格的链接

FileOutputStream os = new FileOutputStream("e:\\workbook.xls");
    wb.write(os);
    os.close();
}

}

2.poi读取excel
package com.test.poi;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Iterator;

import org.apache.poi.hssf.extractor.ExcelExtractor;
import org.apache.poi.hssf.usermodel.HSSFCell;
import org.apache.poi.hssf.usermodel.HSSFRow;
import org.apache.poi.hssf.usermodel.HSSFSheet;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.poifs.filesystem.POIFSFileSystem;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;

public class ReadExcel {

public static void main(String[] args) throws Exception {
    HSSFWorkbook wb = null;
    POIFSFileSystem fs = null;
    try {
      fs = new POIFSFileSystem(new FileInputStream("e:\\workbook.xls"));
      wb = new HSSFWorkbook(fs);
    } catch (IOException e) {
      e.printStackTrace();
    }

HSSFSheet sheet = wb.getSheetAt(0);
    HSSFRow row = sheet.getRow(0);
    HSSFCell cell = row.getCell(0);
    String msg = cell.getStringCellValue();
    System.out.println(msg);
}
public static void method2() throws Exception {

InputStream is = new FileInputStream("e:\\workbook.xls");
    HSSFWorkbook wb = new HSSFWorkbook(new POIFSFileSystem(is));

ExcelExtractor extractor = new ExcelExtractor(wb);
    extractor.setIncludeSheetNames(false);
    extractor.setFormulasNotResults(false);
    extractor.setIncludeCellComments(true);

String text = extractor.getText();
    System.out.println(text);
}

public static void method3() throws Exception {
    HSSFWorkbook wb = new HSSFWorkbook(new FileInputStream("e:\\workbook.xls"));
    HSSFSheet sheet = wb.getSheetAt(0);

for (Iterator<Row> iter = (Iterator<Row>) sheet.rowIterator(); iter.hasNext();) {
      Row row = iter.next();
      for (Iterator<Cell> iter2 = (Iterator<Cell>) row.cellIterator(); iter2.hasNext();) {
        Cell cell = iter2.next();
        String content = cell.getStringCellValue();// 除非是sring类型，否则这样迭代读取会有错误
        System.out.println(content);
      }
    }
}
}

注：HSSFWorkbook，XSSFWorkbook的区别：前者是解析出来excel 2007 以前版本的，后缀名为xls的，后者是解析excel 2007 版的，后缀名为xlsx。

在实际应用中，要对excel文件进行判断，该用哪个workbook来对其进行解析处理，而且，通常把这些方法都做了相应封装，使其更面向对象，上例只是main方法的简单示例而已，仅供参考！