Some methods in the javax.net.ssl package create certificate objects that are not compatible with the certificate objects in the java.security.cert package. This example implements two methods that convert between the two types of certificate objects. 
    // Converts to java.security
    public static java.security.cert.X509Certificate convert(javax.security.cert.X509Certificate cert) {
        try {
            byte[] encoded = cert.getEncoded();
            ByteArrayInputStream bis = new ByteArrayInputStream(encoded);
            java.security.cert.CertificateFactory cf
                = java.security.cert.CertificateFactory.getInstance("X.509");
            return (java.security.cert.X509Certificate)cf.generateCertificate(bis);
        } catch (java.security.cert.CertificateEncodingException e) {
        } catch (javax.security.cert.CertificateEncodingException e) {
        } catch (java.security.cert.CertificateException e) {
        }
        return null;
    }
    
    // Converts to javax.security
    public static javax.security.cert.X509Certificate convert(java.security.cert.X509Certificate cert) {
        try {
            byte[] encoded = cert.getEncoded();
            return javax.security.cert.X509Certificate.getInstance(encoded);
        } catch (java.security.cert.CertificateEncodingException e) {
        } catch (javax.security.cert.CertificateEncodingException e) {
        } catch (javax.security.cert.CertificateException e) {
        }
        return null;
    }