Lab05_AverageStudentsGrades

import java.util.*;

public class Lab05_AverageStudentsGrades {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

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

        int numberOfStudents = Integer.parseInt(scanner.nextLine());

        for (int i = 0; i < numberOfStudents; i++) {
            String[] input = scanner.nextLine().split(" ");

            addStudentsInMap(students, input);
        }

        printFormattedResult(students);

    }

    public static void printFormattedResult(Map<String, List<Double>> students) {
        students.entrySet()
                .stream()
                .forEach(student -> {
                    System.out.printf("%s -> ", student.getKey());

                    student.getValue()
                            .stream()
                            .forEach(e -> System.out.printf("%.2f ", e));

                    double average = 0;

                    for (Double currGrade : student.getValue()) {
                        average = average + currGrade;
                    }
                    average = average / student.getValue().size();

                    System.out.printf("(avg: %.2f)%n", average);

                });
    }

    public static void addStudentsInMap(Map<String, List<Double>> students, String[] input) {
        String name = input[0];
        double grade = Double.parseDouble(input[1]);

        students.putIfAbsent(name, new ArrayList<>());
        students.get(name).add(grade);
    }
}