Security: how to retrieve a certificate from a keystore

See here https://docs.oracle.com/cd/E19509-01/820-3503/ggfen/index.html how to create a keystore with a (self signed) certificate.

Code is here: http://www.java2s.com/Code/Java/Security/RetrievingaCertificatefromaKeyStore.htm

https://docs.oracle.com/javase/7/docs/api/java/security/KeyStore.html

https://docs.oracle.com/javase/7/docs/api/java/security/cert/Certificate.html

http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/6-b14/sun/security/x509/X509CertImpl.java