code: public Proxy setHost( String host )
      {
          if ( this.host.equals( host ) || ( host == null && this.host.length() <= 0 ) )
          {
              return this;
          }
          return new Proxy( type, host, port, auth );
      }
docs: Sets the host of the proxy.
  
  @param host The host of the proxy, may be {@code null}.
  @return The new proxy, never {@code null}.