help me with this class

instructions: The CourseGrade class connects a Professor and a Course with grades. It must have the following: Instance variables:

Professor professor, representing the CourseGrades professor

Course course, representing the CourseGrades course

Map grades, which maps a grade to the number of students who received that grade. The key is a String, rather than a char, because there are grades such as A+ and Other (explained below) that are more than one character. Constructors:

2 A constructor that takes a Professor and Course and sets each instance variable to the respective parameter. It should also initialize grades to a new, empty HashMap. Methods:

Professor getProfessor() that returns the CourseGrades professor

Course getCourse() that returns the CourseGrades course

Map getGrades() that returns the CourseGrades grades

void updateGrade(String grade, int numStudents) that sets grades for the key grade to numStudents. It should overwrite any previously stored grade.

float getAverage() that returns the average GPA for CourseGrade. A grade can be converted to a GPA using this table (found here): A+ A A- B+ B B- C+ C C- D+ D D- F W Other 4.0 4.0 3.7 3.3 3.0 2.7 2.3 2.0 1.7 1.3 1.0 0.7 0.0 0.0 Ignore .Other grades are grades which were not reported for some reason. They should be ignored. For example, a course with 3 students who received an A-, 1 who received a C, 1 who received a W, and 1 who received an Other will have an average GPA of 2.62: (3 ? 3.7) + (1 ? 2.0) + (1 ? 0.0) (3 + 1 + 1) = 2.62 We divide by 5, not 6, because we do not include the Other grade in the average calculation. Note that you do not need to round; just return what you calculated.

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class

public class CourseGrade implements Comparable {

private Professor professor;

private Course course;

private Map grades;

public CourseGrade (Professor professor, Course course) {

throw new UnsupportedOperationException("Remove this line and replace with your implementation.");

}

public Professor getProfessor() {

throw new UnsupportedOperationException("Remove this line and replace with your implementation.");

}

public Course getCourse() {

throw new UnsupportedOperationException("Remove this line and replace with your implementation.");

}

public Map getGrades() {

throw new UnsupportedOperationException("Remove this line and replace with your implementation.");

}

public void updateGrade (String grade, int numStudents) {

throw new UnsupportedOperationException("Remove this line and replace with your implementation.");

}

public float getAverage () {

throw new UnsupportedOperationException("Remove this line and replace with your implementation.");

}

public int getNumGrade (String grade) {

throw new UnsupportedOperationException("Remove this line and replace with your implementation.");

}

public int getNumStudents() {

throw new UnsupportedOperationException("Remove this line and replace with your implementation.");

}

@Override

public int compareTo(CourseGrade o) {

throw new UnsupportedOperationException("Remove this line and replace with your implementation.");

}

}