code: private void addColumn(int index)
      {
          TableColumnModel columnModel = getColumnModel();
          TableColumn column = columnModel.getColumn(index);
          while (tableColumns.size() - 1 < index)
          {
              tableColumns.add(null);
          }
          tableColumns.set(index, column);
          column.addPropertyChangeListener(widthListener);
          
          JComponent component = componentFactory.apply(index);
          while (customComponents.size() - 1 < index)
          {
              customComponents.add(null);
          }
          customComponents.set(index, component);
          add(component);
      }
docs: Add the column and the custom component at the given index
  
  @param index The index