code: @Override
      public synchronized boolean verify(final X509Certificate cert) {
          if (verificationAnswers.containsKey(cert)) {
              return verificationAnswers.get(cert);
          } else {
              boolean answer = delegate.verify(cert);
              verificationAnswers.put(cert, answer);
  
              return answer;
          }
      }
docs: This implementation will forward the given certificate to the delegate
  provided in the constructor, and cache the delegate's response.
  <p>
  On every subsequent invocation with the same certificate, the initial
  response from the delegate will be returned.
  
  @param cert
  the certificate to verify.
  @return the result of calling <tt>verify</tt> on the delegate
  <tt>CertificateVerifier</tt>.