public void initPreemptive(final Credentials credentials) {
        if (credentials != null) {
            Args.check(credentials instanceof UsernamePasswordCredentials,
                    "Unsupported credential type: " + credentials.getClass());
            this.credentials = (UsernamePasswordCredentials) credentials;
            this.complete = true;
        } else {
            this.credentials = null;
        }
    }
Constructs a new BasicScheme with UTF-8 as the charset.

@since 4.3
httpclient5/src/main/java/org/apache/hc/client5/http/impl/auth/BasicScheme.java