Method userSignedOn

java/Chapter 8/Question8_7/UserManager.java:43–49

(String accountName)

	}
	
	public void userSignedOn(String accountName) {
		User user = usersByAccountName.get(accountName);
		if (user != null) {
			user.setStatus(new UserStatus(UserStatusType.Available, ""));			
			onlineUsers.put(user.getId(), user);
		}
	}
	
	public void userSignedOff(String accountName) {
		User user = usersByAccountName.get(accountName);