public void addField(String fldName,Type type){
  fields.put(fldName,type);
  if (myFieldSet != null)   myFieldSet.add(fldName);
}

public void addField ( String fldName , Type type ) { fields . put ( fldName , type ) ; if ( myFieldSet != null ) myFieldSet . add ( fldName ) ; }
adds a field to this schema having a specified name and type .
