Student Roster Java Program, computer science homework help

I finished the first Student class on BlueJ and it compiles just fine. But I cannot figure out how to make the public Roster extends ArrayList<Student> class.public class Student{private String lName, fName;private int idNum;public Student(int id, String fn, String ln){lName = ln;fName = fn;idNum = id;}public String getLastName(){ return lName; }public String getFirstName(){ return fName;}public int getID(){ return idNum;}public String toString(){ return fName + " " + lName + " " + idNum; }}The ArrayList<Student> class must have methods:public boolean contiansStudent(String ln)- given the last name of the student and determines if the student exists in the list.public Student retrieveById(int id)- given the id, finds student in list and returns the student. If student not found, eturn null.public int retrieveId(String ln)- given last name of student, return the id for that student.public boolean addStudent(Student s)- adds the Student s to the list and true or false value that this was accomplished. This method should not allow duplicate students to be added (duplicate meaning same name or id).public boolean removeStudent(int id)- removes a student from the list based on id.public boolean removeStudent(String ln)- removes a student from the list based on last name.public void printRoster()- print all students in the ArrayList<Student> list. Help please!!