public JsonNode put(String fieldName,JsonNode value){
  if (value == null) {
    value=nullNode();
  }
  return _put(fieldName,value);
}

public JsonNode put ( String fieldName , JsonNode value ) { if ( value == null ) { value = nullNode ( ) ; } return _put ( fieldName , value ) ; }
method that will set specified field , replacing old value , if any .
