public void appendColumn(ColumnSpec columnSpec){
  checkNotNull(columnSpec,"The column spec must not be null.");
  colSpecs.add(columnSpec);
}

public void appendColumn ( ColumnSpec columnSpec ) { checkNotNull ( columnSpec , "The column spec must not be null." ) ; colSpecs . add ( columnSpec ) ; }
appends the given column specification to the right hand side of all columns .
