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<pre>public interface <span class="typeNameLabel">Authenticator</span></pre>
<div class="block">Performs either <strong>preemptive</strong> authentication before connecting to a proxy server,
 or <strong>reactive</strong> authentication after receiving a challenge from either an origin web
 server or proxy server.

 <h3>Preemptive Authentication</h3>

 <p>To make HTTPS calls using an HTTP proxy server OkHttp must first negotiate a connection with
 the proxy. This proxy co