05. Average Students Grades

package DPM;

import java.util.*;
import java.util.stream.Collectors;

public class Main {
    public static void main(String[] args){
        Scanner scan = new Scanner(System.in);
        TreeMap<String, List<Double>> students = new TreeMap<>();
        int num = Integer.parseInt(scan.nextLine());

        for (int i = 0; i < num; i++) {
            String[] line = scan.nextLine().split(" ");
            String name = line[0];
            double grade = Double.parseDouble(line[1]);
            students.putIfAbsent(name, new ArrayList<>());
            students.get(name).add(grade);

        }
        students.forEach((name, grades) ->{
            String allGrades = grades.stream()
                    .map(g -> String.format("%.2f", g))
                    .collect(Collectors.joining(" "));
            double avg = grades.stream().mapToDouble(e -> e).average().orElse(0d);
            System.out.println(String.format("%s -> %s (avg: %.2f)", name, allGrades, avg));
        });
    }
}