@Override
  public boolean isEnabledOnElements(PsiElement @NotNull [] elements) {
    return elements.length == 1 &&
           elements[0] instanceof PsiClass &&
           !((PsiClass)elements[0]).isInterface() &&
           elements[0].getLanguage().isKindOf(JavaLanguage.INSTANCE);
  }
@Override
  public boolean isEnabledOnElements(PsiElement @NotNull [] elements)