java程序转换excel中科学记数法的数据为date类型

package excelDemo1;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.OutputStream;
import java.text.DecimalFormat;
import java.util.Date;
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;

/**
 * java读取excel文件及内容
 * 
 * @author tuzongxun123
 *
 */
public class ExcelDemo1 {
    public static void main(String[] args) {
        try {
            // 获取文件在磁盘的存储路径
            File file = new File("C:" + File.separator + "Users"
                    + File.separator + "tuzongxun123" + File.separator
                    + "Desktop" + File.separator + "log.xls");
            // 读文件输入流
            FileInputStream fileInputStream = new FileInputStream(file);
            BufferedInputStream bufferedInputStream = new BufferedInputStream(
                    fileInputStream);
            POIFSFileSystem excelfile = new POIFSFileSystem(bufferedInputStream);
            HSSFWorkbook workbook = new HSSFWorkbook(excelfile);
            // 根据名称获取excel工作薄
            HSSFSheet sheet = workbook.getSheet("Sheet0");
            // 遍历去除工作薄中的行和列
            for (int i = 1;; i++) {
                HSSFRow row = sheet.getRow(i);
                if (row != null) {
                    // 获取科学记数法这一列的单元格
                    HSSFCell cell = row.getCell(6);
                    // 格式化科学计数法的数据格式
                    DecimalFormat df = new DecimalFormat("0");
                    String value = df.format(cell.getNumericCellValue());
                    // 时间转换
                    long long1 = Long.parseLong(value);
                    Date date = new Date(long1);
                    // 创建新的单元格存储转换后的数据
                    HSSFCell cell2 = row.createCell(9);
                    cell2.setCellValue(date);
                } else {
                    break;
                }
            }
            // 把转换后的数据写入到文件中
            OutputStream outputStream = new FileOutputStream(file);
            workbook.write(outputStream);
            outputStream.close();
        } catch (Exception e) {
            e.printStackTrace();
        }

    }
}