### Question:
UrlUtil { @SuppressWarnings("BooleanMethodIsAlwaysInverted") @Contract("null -> false") public static boolean isValidUrl(@Nullable String url) { return isValidUrl(url, ALLOWED_SCHEMES); } private  UrlUtil(); @SuppressWarnings("unused") static Set<String> getParameterNames(@Nonnull String url); @SuppressWarnings("IfStatementWithIdenticalBranches") static String removeParameterFromUrl(@Nonnull String url, @Nullable String parameterName); static String replaceParameterInUrl(
            @Nonnull String url, @Nullable String parameterName, @Nullable String parameterValue); static String appendParameterToUrl(
            @Nonnull String url, @Nullable String parameterName, @Nullable String parameterValue); @SuppressWarnings("OverlyComplexMethod") static String appendParametersToUrl(@Nonnull String url, @Nonnull String... parameterParts); @SuppressWarnings("unused") static String appendRelativePathToUrl(@Nonnull String url, @Nullable String relativePath); @SuppressWarnings("BooleanMethodIsAlwaysInverted") @Contract("null -> false") static boolean isValidUrl(@Nullable String url); @Contract("null, _ -> false") static boolean isValidUrl(@Nullable String url, String[] allowedSchemes); @SuppressWarnings({"ResultOfMethodCallIgnored", "BooleanMethodIsAlwaysInverted"}) @Contract("null -> false") static boolean isValidUri(@Nullable String uri); @SuppressWarnings("unused") @Contract("null -> null") @Nullable static String extractFileName(@Nullable String url);  }### Answer:
@Test public void testIsValidUrl() { assertTrue(UrlUtil.isValidUrl("https: + "%D0%97%D0%B0%D0%B3%D0%BB%D0%B0%D0%B2%D0%BD%D0%B0%D1%8F_%D1%81%D1%82%D1%80%D0%B0%D0%BD%D0%B8%D1%86%D0%B0")); assertTrue(UrlUtil.isValidUrl("http: assertFalse(UrlUtil.isValidUrl(null)); assertFalse(UrlUtil.isValidUrl("")); assertFalse(UrlUtil.isValidUrl("\t")); assertFalse(UrlUtil.isValidUrl(" ")); assertFalse(UrlUtil.isValidUrl(" ")); assertFalse(UrlUtil.isValidUrl("http: }