public static String verifyCertificate(X509Certificate cert,Collection<CRL> crls,Calendar calendar){
  if (SignUtils.hasUnsupportedCriticalExtension(cert))   return "Has unsupported critical extension";
  try {
    cert.checkValidity(calendar.getTime());
  }
 catch (  Exception e) {
    return e.getMessage();
  }
  if (crls != null) {
    for (    CRL crl : crls) {
      if (crl.isRevoked(cert))       return "Certificate revoked";
    }
  }
  return null;
}

public static String verifyCertificate ( X509Certificate cert , Collection < CRL > crls , Calendar calendar ) { if ( SignUtils . hasUnsupportedCriticalExtension ( cert ) ) return "Has unsupported critical extension" ; try { cert . checkValidity ( calendar . getTime ( ) ) ; } catch ( Exception e ) { return e . getMessage ( ) ; } if ( crls != null ) { for ( CRL crl : crls ) { if ( crl . isRevoked ( cert ) ) return "Certificate revoked" ; } } return null ; }
verifies a single certificate .
