public List<Column> columns(String... columnNames){
  List<Column> columns=new ArrayList<>();
  for (  String columnName : columnNames) {
    columns.add(column(columnName));
  }
  return columns;
}

public List < Column > columns ( String ... columnNames ) { List < Column > columns = new ArrayList < > ( ) ; for ( String columnName : columnNames ) { columns . add ( column ( columnName ) ) ; } return columns ; }
returns only the columns whose names are given in the input array
