cas/src/main/java/org/springframework/security/cas/web/CasAuthenticationFilter.java
private boolean authenticated() {
		Authentication authentication = SecurityContextHolder.getContext()
				.getAuthentication();
		return authentication != null && authentication.isAuthenticated()
				&& !(authentication instanceof AnonymousAuthenticationToken);
	}
private boolean authenticated() {
		Authentication authentication = SecurityContextHolder.getContext()
				.getAuthentication();
		return authentication != null && authentication.isAuthenticated()
				&& !(authentication instanceof AnonymousAuthenticationToken);
	}
Determines if a user is already authenticated.
@return