private static void setLongestAsPrototype(@NotNull JComboBox comboBox, @NotNull List<String> variants) {
    Object prototypeDisplayValue = comboBox.getPrototypeDisplayValue();
    String prototypeDisplayValueStr = null;
    if (prototypeDisplayValue instanceof String) {
      prototypeDisplayValueStr = (String)prototypeDisplayValue;
    }
    else if (prototypeDisplayValue != null) {
      return;
    }
    String longest = StringUtil.notNullize(prototypeDisplayValueStr);
    boolean updated = false;
    for (@NlsSafe String s : variants) {
      if (longest.length() < s.length()) {
        longest = s;
        updated = true;
      }
    }
    if (updated) {
      comboBox.setPrototypeDisplayValue(longest);
    }
  }
private static void setLongestAsPrototype(@NotNull JComboBox comboBox, @NotNull List<String> variants)