需求：需要从a.xls文件中读取一列中文数据，存放到b.xls文件中对应的列中去.
图示：a.xls中a列和b列组成数字串对应b.xls中的a列，a.xlsD列写入b.xlsB列
功能实现：
1：处理保存a中数据：

    /**
     * 读excel
     * @param filepath
     * @param sheetNum 工作簿编号0开始第一个工作簿添0，以此类推
     * @throws Exception
     */
    public static void readExcel(String filepath,int sheetNum) throws Exception {
        InputStream inp = new FileInputStream(filepath);
        POIFSFileSystem fs = new POIFSFileSystem(inp);
        Workbook wb = new HSSFWorkbook(fs);
        Sheet sheet = wb.getSheetAt(sheetNum);
        for(int i = sheet.getFirstRowNum();i<=sheet.getLastRowNum();i++) {
            Row row = sheet.getRow(i);
            // 取第一个单元格
            Cell cell = row.getCell(0);
            String pill_preId = "";
            String pill_chname = "";
            if(null != cell) {
                Integer cellV = (int)cell.getNumericCellValue();
                pill_preId = String.format("%02d", cellV);
            }
            // 取第2个单元格
            cell = row.getCell(1);
            if(null != cell) {
                Integer cellV = (int)cell.getNumericCellValue();
                pill_preId = pill_preId+String.format("%02d", cellV);
            }
            // 取第4个单元格
            cell = row.getCell(3);
            if(null != cell) {
                String cellV = cell.getStringCellValue();
                pill_chname = cellV;
            }
            //保存map
            System.out.println("pill_preId: "+pill_preId+" pill_chname: "+pill_chname);
            pillMap.put(pill_preId, pill_chname);
        }              
    }

2：开始插入b表格中

    /**
     * 写入excel
     * @param filename
     * @param sheetNum 工作簿编号0开始第一个工作簿添0，以此类推
     * @throws Exception
     */
    public static void writeExcel(String filename,int sheetNum) throws Exception {
        InputStream inp = new FileInputStream(filename);
        POIFSFileSystem fs = new POIFSFileSystem(inp);
        Workbook wb = new HSSFWorkbook(fs);
        Sheet sheet = wb.getSheetAt(sheetNum);
        for(int i = sheet.getFirstRowNum();i<=sheet.getLastRowNum();i++) {
            Row row = sheet.getRow(i);
            // 取第一个单元格
            Cell cell = row.getCell(0);
            if(null == cell) {
                continue;
            }
            String cellV = cell.getStringCellValue();
            String newV = pillMap.get(cellV);
            //写入第二个单元格
            if(newV != null && !newV.isEmpty()) {
                Cell cell1 = row.getCell(1);
                if(null == cell1) {
                    row.createCell(1);
                }
                cell1.setCellType(CellType.STRING);
                cell1.setCellValue(newV);
            }

        }
        
        FileOutputStream fileOut = new FileOutputStream(filename);
        wb.write(fileOut);
        fileOut.close();
    }

3:单元测试：

    private static Map<String,String> pillMap = new HashMap<>(16);
    
    public static void main(String[] args) throws Exception {
        readExcel("C:\\Users\\user\\Desktop\\pill.xls",0);
        writeExcel("C:\\Users\\user\\Desktop\\POS.xls",0);
    }