HW01_5

import java.io.*;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.function.Supplier;
import java.util.stream.Collectors;
import java.util.stream.Stream;

class Student {
    private String index;
    private List<Subject> subjects;

    public Student(String[] headerParts, String[] rowParts) {
        subjects = new ArrayList<>();
        index = rowParts[0];
        for (int i = 1; i < headerParts.length; i++) {
            subjects.add(new Subject(headerParts[i], Integer.valueOf(rowParts[i])));
        }
    }

    public double getAverage() {
        return subjects.stream()
                .mapToDouble(x -> x.getGrade())
                .average()
                .orElse(0);
    }

    public List<Subject> getSubjects() {
        return subjects;
    }

    @Override
    public String toString() {
        return String.format("%s\t%.2f", index, getAverage());
    }
}

class Subject {
    private String name;
    private Integer grade;

    public Subject(String name, Integer grade) {
        this.name = name;
        this.grade = grade;
    }

    public int getGrade() {
        return grade.intValue();
    }

    public String getName() {
        return name;
    }

    @Override
    public String toString() {
        return String.format("%s\t%d", name, grade);
    }
}

public class HW01_5 {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new FileReader("rezultati.csv"));
        String[] headerParts = reader.readLine().split(",");
        Supplier<Stream<String>> lines = () -> reader.lines();

        List<Student> students = lines.get()
                .map(l -> l.split(","))
                .map(rowParts -> new Student(headerParts, rowParts))
                .collect(Collectors.toList());

        System.out.println("Index\tAverage");
        students.stream()
                .forEach(System.out::println);

        System.out.println("\nCourseName\tAverage");
        students.stream()
                .flatMap(f -> f.getSubjects().stream())
                .collect(Collectors.groupingBy(Subject::getName, Collectors.averagingDouble(Subject::getGrade)))
                .forEach((name, average) -> System.out.println(String.format("%s\t%12.2f", name, average)));
    }
}