code: @Override
    public String format(Object value)
    {
      if(value == null) {
        return "";
      }
      return numberFormat.format(value);
    }
docs: Format numeric value as percent representation using locale settings. Returns empty string if <code>value</code>
  argument is null.
  
  @param value numeric value.
  @return numeric value represented as locale percent or empty string.
  @throws IllegalArgumentException if <code>value</code> argument is not an instance of Number.