Processing X509 certificate, java converts postalCode present in Subject line to its OID value

Question

When converting an uploaded security certificate to X509 format and later obtaining the subject line through following code. eg

cert = (X509Certificate) cf.generateCertificate(inStream);
String subject =cert.getSubjectX500Principal().toString().toUpperCase();

I find that the java X500Principal() converts postalCode to its OID value OID.2.5.4.17.

Is there any way that the object name 'postalCode' can be retained or OID can be converted back to its user friendly format.