java poi 导入excel时 读取单元格内容的方法 ，其中包含excel中有函数的读法

public static String getExcelCellValue(Cell cell) {
		String ret = "";
		try {
			if (cell == null) {
				ret = "";
			} else if (cell.getCellType() == HSSFCell.CELL_TYPE_STRING) {
				ret = cell.getStringCellValue().trim();
			} else if (cell.getCellType() == HSSFCell.CELL_TYPE_NUMERIC) {
				if (HSSFDateUtil.isCellDateFormatted(cell)) {
					Date date = cell.getDateCellValue();
					ret = DateFormatUtils.format(date, "yyyy-MM-dd HH:mm:ss SSS");
				} else {
					ret = NumberToTextConverter.toText(cell.getNumericCellValue());
					String temp = ret.substring(ret.indexOf(".") + 1, ret.length());
					try {
						if (Integer.parseInt(temp) == 0) {
							ret = ret.substring(0, ret.indexOf("."));
						}
					} catch (Exception ex) {
					}
				}
			} else if (cell.getCellType() == HSSFCell.CELL_TYPE_FORMULA) {//有公式的Excel单元格
				//这样对于字符串cell.getStringCellValue()方法即可取得其值，如果公式生成的是数值，使用cell.getStringCellValue()方法会抛出IllegalStateException异常，在异常处理中使用cell.getNumericCellValue();即可。
				try {  
					ret = String.valueOf(cell.getStringCellValue());  
				} catch (IllegalStateException e) {  
					ret = String.valueOf(cell.getNumericCellValue());  
				}
			} else if (cell.getCellType() == HSSFCell.CELL_TYPE_ERROR) {
				ret = "" + cell.getErrorCellValue();
			} else if (cell.getCellType() == HSSFCell.CELL_TYPE_BOOLEAN) {
				ret = "" + cell.getBooleanCellValue();
			} else if (cell.getCellType() == HSSFCell.CELL_TYPE_BLANK) {
				ret = "";
			}
		} catch (Exception ex) {
			ex.printStackTrace();
			ret = "";
		}
		return ret;
	}