@Override
        public String toString() {
            final StringBuilder buf = new StringBuilder();
            buf.append(scheme).append("://").append(host);
            if (port >= 0) {
                buf.append(":").append(port);
            }
            if (pathPrefix != null) {
                if (!pathPrefix.startsWith("/")) {
                    buf.append("/");
                }
                buf.append(pathPrefix);
            }
            return buf.toString();
        }
Default implementation of {@link AuthCache}. This implements
expects {@link AuthScheme} to be {@link Serializable}
in order to be cacheable.
<p>
Instances of this class are thread safe as of version 4.4.
</p>

@since 4.1
httpclient5/src/main/java/org/apache/hc/client5/http/impl/auth/BasicAuthCache.java