code: public static String formatDouble(final Double amount, String pattern) {
  		if (pattern == null || pattern.equals("")) {
  			pattern = JKFormatUtil.DEFAULT_DOUBLE_FORMAT;
  		}
  		return JKFormatUtil.getNumberFormatter(pattern).format(amount);
  	}
docs: Format double.
  
  @param amount  the amount
  @param pattern the pattern
  @return the string