public void addItem(final @NotNull GroupItem group, final @NotNull ComponentItem item) {
    // class -> item
    final String componentClassName = item.getClassName();
    if (getItem(componentClassName) != null) {
      Messages.showMessageDialog(
        UIDesignerBundle.message("error.item.already.added", componentClassName),
        ApplicationNamesInfo.getInstance().getFullProductName(),
        Messages.getErrorIcon()
      );
      return;
    }
    myClassName2Item.put(componentClassName, item);

    // group -> items
    group.addItem(item);

    // Process special predefined item for JPanel
    if ("javax.swing.JPanel".equals(item.getClassName())) {
      myPanelItem = item;
    }
  }
public void addItem(final @NotNull GroupItem group, final @NotNull ComponentItem item)