code: private byte[] maybeDecodeBase64(byte[] byteArray) {
      try {
        String pem = new String(byteArray);
        // Remove required begin/end lines.
        pem = pem.substring(BEGIN_CERT_LINE_LENGTH, pem.length() - END_CERT_LINE_LENGTH);
        return Base64.getDecoder().decode(pem);
      } catch (Exception e) {
        // Not a valid PEM encoded certificate, return original array.
        return byteArray;
      }
    }
docs: Test whether array is a Base64-encoded certificate. If so, return
  the decoded content instead of the specified array.
  
  @see CertificateFactorySpi#engineGenerateCertificate(InputStream)