03. Inbox Manager

import java.util.*;
public class zad3_FinalExam_7Dec {


    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);

        String input = scanner.nextLine();

        Map<String, List<String>> messagesMap = new LinkedHashMap<>();
        Map<String, Integer> messagesCountMap = new LinkedHashMap<>();

        while(!input.equals("Statistics")){

            String[] inputArray = input.split("->");

            switch (inputArray[0]){

                case"Add":

                    String addUsername = inputArray[1];

                    if(messagesMap.containsKey(addUsername)){

                        System.out.println(addUsername+" is already registered");

                    }else{

                        List<String> messagesList = new ArrayList<>();
                        messagesMap.put(addUsername, messagesList);
                        messagesCountMap.put(addUsername, 0);
                    }

                    break;

                case"Send":

                    String senderUsername = inputArray[1];
                    String email = inputArray[2];

                    messagesMap.get(senderUsername).add(email);
                    messagesMap.replace(senderUsername, messagesMap.get(senderUsername));
                    messagesCountMap.replace(senderUsername, messagesCountMap.get(senderUsername)+1);

                    break;

                case"Delete":

                    String deleteUsername = inputArray[1];

                    if(messagesMap.containsKey(deleteUsername)) {

                        messagesMap.remove(deleteUsername);
                        messagesCountMap.remove(deleteUsername);

                    }else{

                        System.out.println(deleteUsername+" not found!");
                    }
                    break;

            }

            input = scanner.nextLine();
        }

        int usersCount = messagesMap.size();

        System.out.println("Users count: "+usersCount);

        messagesCountMap.entrySet().stream().sorted((a,b)-> {

            int res = b.getValue().compareTo(a.getValue());

            if(res == 0){

                res = a.getKey().compareTo(b.getKey());
            }

            return res;

        }).forEach(entry -> {

            String username = entry.getKey();

            System.out.println(username);

            for(String currentEmail : messagesMap.get(username)){

                System.out.println(String.format(" - %s",currentEmail));
            }

        });

    }
}