User Logs

package a031_SetsAndMaps_Advanced_Ex;

import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Scanner;
import java.util.TreeMap;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class P09_UserLogs {
    public static void main(String[] args) {
        @SuppressWarnings("resource")

        Scanner sc = new Scanner(System.in);

        Map<String, Map<String, List<String>>> userLogs = new TreeMap<>();

        String line = "";

        String regex = "IP=(?<ip>[\\w.:]+)\\smessage=(?<mess>.+)\\suser=(?<user>\\w+)";
        Pattern pattern = Pattern.compile(regex);

        while (!"end".equals(line = sc.nextLine())) {
            Matcher matcher = pattern.matcher(line);

            if (matcher.find()) {
                String user = matcher.group("user");
                String ip = matcher.group("ip");
                String message = matcher.group("mess");

                userLogs.putIfAbsent(user, new LinkedHashMap<>());
                userLogs.get(user).putIfAbsent(ip, new ArrayList<>());
                userLogs.get(user).get(ip).add(message);
            }
        }

        userLogs.entrySet().stream().forEach(user -> {
            List<String> output = new ArrayList<>();
            System.out.println(user.getKey() + ":");
            user.getValue().entrySet().stream().forEach(ip -> {
                output.add((String.format("%s => %d", ip.getKey(), ip.getValue().size())));
            });

            System.out.println(output.toString().replaceAll("\\]|\\[", "") + ".");
        });
    }
}