code: public PrivateKey getPrivateKey()
  	throws GSSException {
          try {
  	    return (this.cred == null) ? null : this.cred.getPrivateKey();
  	} catch (CredentialException e) {
              throw new GlobusGSSException(GSSException.FAILURE, e);
          }
      }
docs: Returns the private key of this credential (if any).
  
  @return The private key. Might be null if this
  is an anonymous credential.