public void addColumn(Column previousColumn,Column column){
  if (column != null) {
    if (previousColumn == null) {
      columns.add(0,column);
    }
 else {
      columns.add(columns.indexOf(previousColumn),column);
    }
  }
}

public void addColumn ( Column previousColumn , Column column ) { if ( column != null ) { if ( previousColumn == null ) { columns . add ( 0 , column ) ; } else { columns . add ( columns . indexOf ( previousColumn ) , column ) ; } } }
adds the column after the given previous column .
