Need this in Java Domain class called studentRoster that maintains a list of Student that are registered in a particular course. Implement a method for adding new students to the list.Create 2 view classes. The first view class is called ViewAverageGrade and its only purpose is to display the average grade of all students currently in the roster. The second class is called ViewStudentsFailedClass its only purpose is to display the number of students that have a failing grade. Most importantly , Implement the observer-observable pattern so that that View classes always display the most current information every time the roster is updated. Implement a main method to test your implementation. Add comments