Pobranie wartości pola z innej klasy oraz filtrowanie mapy za pomocą lambdy. [JAVA]

pytanie zadane 22 czerwca 2017 w Java przez Szymon Ciamaga Obywatel (1,980 p.)

Witam mam klasę student która reprezentuje studenta mam także klasę Grade która reprezentuje stopnie na studiach

do tego w jednej z klas chce chce pobrać imię i nazwisko studenta ale także jego stopień i zapisać do mapy następnie chce znaleźć najwyższe oceny końcowe z tych przedmiotów

public class Student extends Person implements IStudent {

    private String indexNumber;

    private Specialization specialization;

    private int ageStudies;

    private Yearbook yearbook;

    private List<Grade> gradeList = new ArrayList<>();

    public String getIndexNumber() {
        return indexNumber;
    }

    public void setIndexNumber(String indexNumber) {
        this.indexNumber = indexNumber;
    }

    @Override
    public Specialization getSpecialization() {
        return specialization;
    }

    @Override
    public String getStudentFirstName() {
        return getFirstName();
    }

    @Override
    public String getStudentSurname() {
        return getSurname();
    }

    public Yearbook getYearbook() {
        return yearbook;
    }

    public void setYearbook(Yearbook yearbook) {
        this.yearbook = yearbook;
    }

    public void setSpecialization(Specialization specialization) {
        this.specialization = specialization;
    }

    public int getAgeStudies() {
        return ageStudies;
    }

    public void setAgeStudies(int ageStudies) {
        this.ageStudies = ageStudies;
    }

    public List<Grade> getGradeList() {
        return gradeList;
    }

    public void setGradeList(List<Grade> gradeList) {
        this.gradeList = gradeList;
    }

public class Grade {

    private int gradeFinal;

    private Subject subject;

    private List<Integer> gradeList = new ArrayList<>();

    private double average;

    public int getGradeFinal() {
        return gradeFinal;
    }

    public void setGradeFinal(int gradeFinal) {
        this.gradeFinal = gradeFinal;
    }

    public Subject getSubject() {
        return subject;
    }

    public void setSubject(Subject subject) {
        this.subject = subject;
    }

    public List<Integer> getGradeList() {
        return gradeList;
    }

    public void setGradeList(List<Integer> gradeList) {
        this.gradeList = gradeList;
    }

    public double getAverage() {
        return average;
    }

    public void setAverage(double average) {
        this.average = average;
    }

    public Grade(int gradeFinal, Subject subject, List<Integer> gradeList, double average) {
        this.gradeFinal = gradeFinal;
        this.subject = subject;
        this.gradeList = new ArrayList<>(gradeList);
        this.average = average;
    }

    public void whoHasTheBestScoreFromTheSubject() {
        Map<Integer, String> grades = new HashMap<>();

        for (int i = 0; i < studentList.size(); i++) {
            IStudent student = studentList.get(i);
            String firstName = student.getStudentFirstName();
            String surname = student.getStudentSurname();

            Integer finalGrade = student.getStudentFinalGrade();
            grades.put(finalGrade, firstName + " " + surname);
            grades.forEach((a, b) -> System.out.println(a + " " + b));
        }
    }

dodam że