private void processFirstItem(@Nullable JdkComboBoxItem firstItem) {
    if (firstItem instanceof ProjectJdkComboBoxItem) {
      myModel.showProjectSdkItem();
    } else if (firstItem instanceof NoneJdkComboBoxItem) {
      myModel.showNoneSdkItem();
    } else if (firstItem instanceof ActualJdkComboBoxItem) {
      setSelectedJdk(((ActualJdkComboBoxItem)firstItem).myJdk);
    }
  }
private void processFirstItem(@Nullable JdkComboBoxItem firstItem)