java使用XSSFWorkbook实现读写Excel

        <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi-ooxml</artifactId>
            <version>4.1.2</version>
        </dependency>

 /**
     * 读取Excel文件的内容
     * @param inputStream excel文件，以InputStream的形式传入
     * @param sheetName sheet名字
     * @return 以List返回excel中内容
     */
    public static List<Map<String, String>> readExcel(InputStream inputStream, String sheetName) {

        //定义工作簿
        XSSFWorkbook xssfWorkbook = null;
        try {
            xssfWorkbook = new XSSFWorkbook(inputStream);
        } catch (Exception e) {
            System.out.println("Excel data file cannot be found!");
        }

        //定义工作表
        XSSFSheet xssfSheet;
        if (sheetName.equals("")) {
            // 默认取第一个子表
            xssfSheet = xssfWorkbook.getSheetAt(0);
        } else {
            xssfSheet = xssfWorkbook.getSheet(sheetName);
        }

        List<Map<String, String>> list = new ArrayList<Map<String, String>>();

        //定义行
        //默认第一行为标题行，index = 0
        XSSFRow titleRow = xssfSheet.getRow(0);

        //循环取每行的数据
        for (int rowIndex = 1; rowIndex < xssfSheet.getPhysicalNumberOfRows(); rowIndex++) {
            XSSFRow xssfRow = xssfSheet.getRow(rowIndex);
            if (xssfRow == null) {
                continue;
            }

            Map<String, String> map = new LinkedHashMap<String, String>();
            //循环取每个单元格(cell)的数据
            for (int cellIndex = 0; cellIndex < xssfRow.getPhysicalNumberOfCells(); cellIndex++) {
                XSSFCell titleCell = titleRow.getCell(cellIndex);
                XSSFCell xssfCell = xssfRow.getCell(cellIndex);
                map.put(getString(titleCell),getString(xssfCell));
            }
            list.add(map);
        }
        return list;
    }

    /**
     * 把单元格的内容转为字符串
     * @param xssfCell 单元格
     * @return 字符串
     */
    public static String getString(XSSFCell xssfCell) {
        if (xssfCell == null) {
            return "";
        }
        if (xssfCell.getCellTypeEnum() == CellType.NUMERIC) {
            return String.valueOf(xssfCell.getNumericCellValue());
        } else if (xssfCell.getCellTypeEnum() == CellType.BOOLEAN) {
            return String.valueOf(xssfCell.getBooleanCellValue());
        } else {
            return xssfCell.getStringCellValue();
        }
    }

    /**
     * 把内容写入Excel
     * @param list 传入要写的内容，此处以一个List内容为例，先把要写的内容放到一个list中
     * @param outputStream 把输出流怼到要写入的Excel上，准备往里面写数据
     */
    public static void writeExcel(List<List> list, OutputStream outputStream) {
        //创建工作簿
        XSSFWorkbook xssfWorkbook = null;
        xssfWorkbook = new XSSFWorkbook();

        //创建工作表
        XSSFSheet xssfSheet;
        xssfSheet = xssfWorkbook.createSheet();

        //创建行
        XSSFRow xssfRow;

        //创建列，即单元格Cell
        XSSFCell xssfCell;

        //把List里面的数据写到excel中
        for (int i=0;i<list.size();i++) {
            //从第一行开始写入
            xssfRow = xssfSheet.createRow(i);
            //创建每个单元格Cell，即列的数据
            List sub_list =list.get(i);
            for (int j=0;j<sub_list.size();j++) {
                xssfCell = xssfRow.createCell(j); //创建单元格
                xssfCell.setCellValue((String)sub_list.get(j)); //设置单元格内容
            }
        }

        //用输出流写到excel
        try {
            xssfWorkbook.write(outputStream);
            outputStream.flush();
            outputStream.close();
        }catch (IOException e) {
            e.printStackTrace();
        }

    }

public static List<List> convertMapToList(Map map) {
        List<List> list = new ArrayList<List>();
        List<String> key_list = new LinkedList<String>();
        List<String> value_list = new LinkedList<String>();

        Set<Entry<String,String>> set = map.entrySet();
        Iterator<Entry<String,String>> iter1 = set.iterator();
        while (iter1.hasNext()) {
            key_list.add(iter1.next().getKey());
        }
        list.add(key_list);

        Collection<String> value = map.values();
        Iterator<String> iter2 = value.iterator();
        while (iter2.hasNext()) {
            value_list.add(iter2.next());
        }
        list.add(value_list);
        return list;
    }