Method sendMessageToUser

java/Chapter 8/Question8_7/User.java:25–33

(User toUser, String content)

	}
	
	public boolean sendMessageToUser(User toUser, String content) {
		PrivateChat chat = privateChats.get(toUser.getId());
		if (chat == null) {
			chat = new PrivateChat(this, toUser);
			privateChats.put(toUser.getId(), chat);
		}
		Message message = new Message(content, new Date());
		return chat.addMessage(message);
	}
	
	public boolean sendMessageToGroupChat(int groupId, String content) {
		GroupChat chat = groupChats.get(groupId);