关于jxl的问题

Question

WritableWorkbook中write方法可以用来对xls文件写操作
但只能写一次，下面的写操作好像无效了
有什么方法可以实现来一次数据写一次，从而实现动态写操作？？

Answer 1

是否write方法中的对象传递了错误的引用

Answer 2

public class ExcelUtil {    public WritableSheet createWritableSheet(String sheetname) throws IOException {
        if (null==writableWorkbook){
            writableWorkbook = Workbook.createWorkbook(new File(filename));
        }        WritableSheet sheet = writableWorkbook.getSheet(sheetname);
        if (null!=sheet){
            throw new IOException(sheetname + " exists in " + filename);
        }
        sheet = writableWorkbook.createSheet(sheetname, 0);        return sheet;
    }
    public int writeHeader2sheet(WritableSheet sheet, List<String> headerData)
      throws WriteException,IOException {
      int count = 0;        List<String> data = headerData;        for (int j = 0; j < data.size(); j++) {
          //format
          jxl.write.WritableCellFormat wcf = new jxl.write.WritableCellFormat();
          wcf.setWrap(true);
          wcf.setAlignment(jxl.format.Alignment.CENTRE);
          wcf.setVerticalAlignment(jxl.format.VerticalAlignment.CENTRE);
          jxl.write.WritableFont wf = new jxl.write.WritableFont(WritableFont.TIMES,
                  10, WritableFont.BOLD, true);
          wcf.setFont(wf);          //Label(列号,行号 ,内容 )
          jxl.write.Label colData = new jxl.write.Label(j, 0,data.get(j),wcf); 
          sheet.addCell(colData);
        }        count++;      rowCount = rowCount + count;      return count;
    }
    public int writeData2sheet(WritableSheet sheet, int start, List<List<String>> rowData)
      throws WriteException,IOException {
      int count = 0;      for (int i = 0; i < rowData.size(); i++) {
        List<String> data = rowData.get(i);        //row height
        sheet.setRowView(rowCount+i, 500*4);        for (int j = 0; j < data.size(); j++) {
          //format
          jxl.write.WritableCellFormat wcf = new jxl.write.WritableCellFormat();
          wcf.setWrap(true);
          wcf.setAlignment(jxl.format.Alignment.LEFT);
          wcf.setVerticalAlignment(jxl.format.VerticalAlignment.CENTRE);          //column width
          sheet.setColumnView(j, j==0?10:50);          //Label(列号,行号 ,内容 )
          jxl.write.Label colData = new jxl.write.Label(j, rowCount + start + i,data.get(j),wcf);  
          sheet.addCell(colData);
        }        count++;
      }      rowCount = rowCount + count;      return count;
    }    public void close() throws IOException,WriteException {
        if (null!=writableWorkbook){
            writableWorkbook.write(); 
            writableWorkbook.close();
            writableWorkbook = null;
        }
    }    public int writeData2sheet(WritableSheet sheet, List<List<String>> rowData)
    throws Exception {
        return writeData2sheet(sheet, 0, rowData);
    }
    
    public void write() throws IOException,WriteException{
     if (null!=writableWorkbook){
            writableWorkbook.write();         }
    }    public static void main(String[] args) {
        try {
            List<List<String>> allData = new ArrayList<List<String>>();
            List<String> data = new ArrayList<String>();
            int start = (int)System.currentTimeMillis()&0xffff;
            for (int i = start; i < start+10; i++) {
                data.add(String.valueOf(i));
            }
            allData.add(data);            ExcelUtil excelUtil = new ExcelUtil("test.xls");
            WritableSheet writableSheet = excelUtil.createWritableSheet(TextFormat.getDateTime(TextFormat.YYYYMMDD+TextFormat.HHMMSS));            int count = excelUtil.writeHeader2sheet(writableSheet, data);
            excelUtil.write();//这个能正常写入            count = excelUtil.writeData2sheet(writableSheet, allData);
            excelUtil.write();//这个不能正常写入        } catch (Exception e) {
            e.printStackTrace();
        }
    }}

Answer 3

每次写入 都new一次 应该没问题
WritableWorkbook workBook = Workbook.createWorkbook(new File(file));