private @NotNull List<String> getPossibleFqns(@NotNull PsiQualifiedReferenceElement ref) {
    Collection<String> fqns = getFqns(ref);

    List<String> res = new ArrayList<>(fqns.size());

    for (String fqn : fqns) {
      if (fqn.startsWith("java.") || fqn.startsWith("javax.swing.")) {
        continue;
      }
      int index = fqn.lastIndexOf('.');
      if (index == -1) {
        continue;
      }
      String className = fqn.substring(index + 1);
      if (className.isEmpty() || Character.isLowerCase(className.charAt(0))) {
        continue;
      }

      res.add(fqn);
    }

    return res;
  }
private @NotNull List<String> getPossibleFqns(@NotNull PsiQualifiedReferenceElement ref)