code: public final Certificate getCertificate(String alias)
          throws KeyStoreException
      {
          if (!initialized) {
              throw new KeyStoreException("Uninitialized keystore");
          }
          return keyStoreSpi.engineGetCertificate(alias);
      }
docs: Returns the certificate associated with the given alias.
  
  <p> If the given alias name identifies an entry
  created by a call to <code>setCertificateEntry</code>,
  or created by a call to <code>setEntry</code> with a
  <code>TrustedCertificateEntry</code>,
  then the trusted certificate contained in that entry is returned.
  
  <p> If the given alias name identifies an entry
  created by a call to <code>setKeyEntry</code>,
  or created by a call to <code>setEntry</code> with a
  <code>PrivateKeyEntry</code>,
  then the first element of the certificate chain in that entry
  is returned.
  
  @param alias the alias name
  
  @return the certificate, or null if the given alias does not exist or
  does not contain a certificate.
  
  @exception KeyStoreException if the keystore has not been initialized
  (loaded).