Student.java

public class Student {
    private int id;
    private String name;
    private int[] marks;
    private float average;
    private char grade;

    public Student(int id, String name, int[] marks) {
        this.id = id;
        this.name = name;
        this.marks = marks;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int[] getMarks() {
        return marks;
    }

    public void setMarks(int[] marks) {
        this.marks = marks;
    }

    public float getAverage() {
        return average;
    }

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

    public char getGrade() {
        return grade;
    }

    public void setGrade(char grade) {
        this.grade = grade;
    }

    public void calculateAvg() {
        int total = 0;

        for (int mark : marks) {
            total += mark;
        }

        average = (float) total / (float) marks.length;
    }

    public void findGrade() {
        if (average <= 100 && average >= 80) {
            grade = 'O';
        } else if (average < 80 && average >= 50) {
            grade = 'A';
        }

        for (int mark : marks) {
            if (mark < 50) {
                grade = 'F';
            }
        }
    }
}