Student.java

package set;

import java.util.Objects;

public class Student implements Comparable<Student> {
    private String name;
    private int course;

    public Student(String name, int course) {
        this.name = name;
        this.course = course;
    }

    @Override
    public int compareTo(Student o) {
        return (this.course-o.course);
    }

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", course=" + course +
                '}';
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Student student = (Student) o;
        return course == student.course;
    }

    @Override
    public int hashCode() {
        return Objects.hash(course);
    }
}