code: public String getValue(Object o, String dateFormat)
      {
          String ret = "null";
          if(o != null)
          {
              if(o instanceof java.lang.Number)
              {
                  ret = o.toString();
                  if(type == NO_TYPE)
                      type = NUMBER_TYPE;
                  if(inputType != NO_TYPE)
                      ret = convert(ret, dateFormat);
              }
              else if(o instanceof java.lang.Boolean)
              {
                  ret = o.toString();
                  if(type == NO_TYPE)
                      type = BOOLEAN_TYPE;
              }
              else if(o instanceof Date)
              {
                  Date dt = (Date)o;
                  ret = Long.toString(dt.getTime());
                  if(type == NO_TYPE)
                      type = DATETIME_TYPE;
                  if(format.length() == 0)
                      format = new String(dateFormat);
              }
              else
              {
                  ret = o.toString().trim();
                  if(type == NO_TYPE)
                      type = STRING_TYPE;
                  if(!(o instanceof String))
                      logger.severe("invalid file column type="+o.getClass().getName());
                  if(inputType != NO_TYPE)
                      ret = convert(ret, dateFormat);
              }
          }
          else // Cell contains null
          {
              // Replace null item with default string
              if(nullValue != null)
                  ret = new String(nullValue);
          }
  
          return ret;
      }
docs: Returns the formatted object for the given cell.
  @param o The value of the cell
  @param dateFormat The date format to use if the cell contains a date
  @return The formatted object for the given cell