public static String appendScheme(final String url, final String scheme) {
        String schemeUrl = url;
        if (!schemeUrl.startsWith("http://") && !schemeUrl.startsWith("https://")) {
            schemeUrl = scheme + "://" + schemeUrl;
        }
        return schemeUrl;
    }
@Test
    void appendScheme() {
        String uri = UriUtils.appendScheme("example.com", "http");
        assertEquals("http://example.com", uri);

        uri = UriUtils.appendScheme("example.com", "https");
        assertEquals("https://example.com", uri);

        uri = UriUtils.appendScheme("https://example.com", "http");
        assertEquals("https://example.com", uri);
        assertNotEquals("http://example.com", uri);

        uri = UriUtils.appendScheme("http://example.com", "https");
        assertEquals("http://example.com", uri);
        assertNotEquals("https://example.com", uri);
    }