使用jxl.jar处理excel文档，创建的excel文件不能写入数据

使用jxl.jar的createWorkbook方法对excel文件不能写入数据？实例代码如下：

/**

 *

 */

package zte.schedule;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.OutputStream;

import jxl.Workbook;

import jxl.write.WritableSheet;

import jxl.write.WritableWorkbook;

import jxl.write.WriteException;

import jxl.write.biff.RowsExceededException;

/**

 * @包名 zte.schedule

 * @文件名 testjxl.java

 * @创建日期 2013-3-16

 * @版本 V 1.0

 */

public class testjxl {

 public static void main(String[] args) {

  String targetfile = "c:/out.xls";// 输出的excel文件名

  String worksheet = "List";// 输出的excel文件工作表名

  String[] title = { "ID", "NAME", "DESCRIB" };// excel工作表的标题

  Workbook workbook1 = null;

  WritableWorkbook workbook = null;

  // 创建可写入的Excel工作薄,运行生成的文件在tomcat/bin下

  // workbook = Workbook.createWorkbook(new File("output.xls"));

  System.out.println("begin");

  OutputStream os = null;

  try {

   os = new FileOutputStream(targetfile);

  } catch (FileNotFoundException e) {

   // TODO Auto-generated catch block

   e.printStackTrace();

  }

  try {

   workbook = Workbook.createWorkbook(os);

   String apiVersion = workbook1.getVersion();

   System.out.println(apiVersion);

  } catch (IOException e) {

   // TODO Auto-generated catch block

   e.printStackTrace();

  }

  WritableSheet sheet = workbook.createSheet(worksheet, 0); // 添加第一个工作表

  // WritableSheet sheet1 = workbook.createSheet("MySheet1", 1);

  // //可添加第二个工作

  jxl.write.Label label;

  for (int i = 0; i < title.length; i++) {

   // Label(列号,行号 ,内容 )

   label = new jxl.write.Label(i, 0, title[i]); // put the title in

               // row1

   try {

    sheet.addCell(label);

   } catch (RowsExceededException e) {

    // TODO Auto-generated catch block

    e.printStackTrace();

   } catch (WriteException e) {

    // TODO Auto-generated catch block

    e.printStackTrace();

   }

  }

 }

}