package StudentPkg;

/**
 * StudentGrades.java
 * Created on September 20, 2001, 11:03 AM
 * This class processes student grades
 *
 * @author  Stuart Hansen
 * @version 
 **/

import java.util.*;
import java.io.*;
public class StudentGrades {
    private Vector studentVector = new Vector();  // A vector containing all the students
    
    // Create an empty set of student grades */
    public StudentGrades() {}
    
    /** add a student to the class list **/
    public void add(Student s) {
        studentVector.add(s);
    }

    /** returns the number of students in the object */
    public int getStudentCount() {return studentVector.size();}
    
    /** returns the student at index i in the vector */
    public Student getStudent(int i) {return (Student)studentVector.get(i);}

    /** returns the average of the student averages **/
    public double getAverage () {
        double sum = 0.0;
        for (Iterator i= studentVector.iterator(); i.hasNext();) {
            sum += ((Student)(i.next())).getAverage();
        }
        return sum/studentVector.size();
    }

    /** returns the exam average for the given exam **/
    public double getExamAverage(int exam) {
        if (exam == 1) 
	    return getExam1Average();
        else if (exam == 2)
            return getExam2Average();
        else if (exam ==3)
            return getExam3Average();
        return 0;
    }

    /** returns the average for exam 1 **/
    public double getExam1Average() {
        double sum = 0.0;
        for (int i=0; i<studentVector.size(); i++) 
            sum += getStudent(i).getExam1();
        return sum/studentVector.size();
    }

    /** returns the average for exam 2 **/
    public double getExam2Average() {
        double sum = 0.0;
        for (int i=0; i<studentVector.size(); i++) 
            sum += getStudent(i).getExam2();
        return sum/studentVector.size();
    }

    /** returns the average for exam 3 **/
    public double getExam3Average() {
        double sum = 0.0;
        for (int i=0; i<studentVector.size(); i++) 
            sum += getStudent(i).getExam3();
        return sum/studentVector.size();
    }

    /** returns the sample standard deviation of the student averages **/
    public double getStandDev() {
        double avg = getAverage();  // The class average
        double sumOfDevSq = 0.0;    // an accumulator
        for (Iterator i= studentVector.iterator(); i.hasNext();) {
            double temp = ((Student)(i.next())).getAverage() - avg;
            sumOfDevSq += temp*temp;
        }
        return Math.sqrt(sumOfDevSq/(studentVector.size()-1));
    }
        
    /** prints all the students. **/
    public void printStudents () {
        for (int i= 0; i< studentVector.size(); i++) {
            System.out.println ((Student)studentVector.elementAt(i));
        }
    }

    /** writes all students to a file **/
    public void printStudentsToFile (String filename) throws IOException {
       FileOutputStream fileOut = new FileOutputStream (filename);
       PrintWriter writer = new PrintWriter(fileOut);

       for (Iterator i = studentVector.iterator(); i.hasNext(); ) {
           Student stemp = (Student) i.next();
           writer.println (stemp.getName() + "\n" + stemp.getExam1() + " " + stemp.getExam2()
                                           + " " + stemp.getExam3 () );
       }

       writer.flush();
       writer.close();
    }

  
}