code: private void writeDoubleField(String fieldName, Object value) throws IOException
     {
        double val = ((Number) value).doubleValue();
        if (val != 0)
        {
           m_writer.writeNameValuePair(fieldName, val);
        }
     }
docs: Write an double field to the JSON file.
  
  @param fieldName field name
  @param value field value