Question

Lab 3 Java Classes and Memory Management

Multi-file Project

1. In this lab you will gain experience using classes and arrays of classes. Use the following as the beginning of a student abstract data type.

public class Student

{

private String fName ;

private String lName ;

private double[] grades;

}

This class should be in the package com.csc241. Write a program that prompts a user for a total number of students and dynamically allocates memory for just that number of Student objects in a Student[]. Then continuously re-prompt the user to enter, on a studentbystudent basis,

1. a student’s first and last name to be used in populating the class data members fName and lName with appropriate set methods. Use local String variables to hold the values entered by the user.
2. the number of grades for the student to be stored in nGrds, a local variable of the main program.

Next,

3. dynamically allocate memory for the grades and assign the resulting reference to a local double[]. Prompt the user for the nGrds values and after acquiring them all, assign the local grades array to the Student instance in the array using an appropriate set method.
4. re-use the MaxMin class you wrote in a previous lab, but also put it in the package com.csc241. Similarly, the GradeCalculator class that you created in the last assignment needs to be in the com.csc241 package. You will be using the avg and maxMin static methods that accept the grades[] in order to compute individual student statistics.
5. In order for you to calculate ensemble statistics, that is statistics for the entire class, the GradeCalculator class will need methods avg and maxMin that accept as an argument the Student[] that you dynamically allocated. These methods must loop through the individual grades[] of each Student array element in order to compute the total class average, max and min values.
6. display the results to the user, both on a per student and ensemble basis. Your output should appear as shown below. Please make note of and reproduce all the decimal formatting and other characteristics of the sample output.

As always, keep in mind all of the general rules of good program construction.

How many students are in your class - 3

Enter the first name of student #1 - Joe

Enter Mike’s last name - Shmo

How many grades will you be entering for Joe Shmo? – 5

Plz enter the grades for Joe Shmo

100

97

87

87

92

Grade Statistics for Joe Shmo (average=92.6 ; max/min=100/87)

Enter the first name of student #2 - Jack

Enter Jack’s last name - Schwartz

How many grades will you be entering for Jack Schwartz? – 3

Plz enter the grades for Jack Schwartz

100

90

0

Grade Statistics for Jack Schwartz (average=63.3 ; max/min=100/0)

Enter the first name of student #3 - Joan

Enter Joan’s last name - Jameson

How many grades will you be entering for Joan Jameson? – 4

Plz enter the grades for Joan Jameson

98

95

93

94

Grade Statistics for Joan Jameson (average=95.0 ; max/min=98/93)

Ensemble Statistics - Average=86.1 ; Max/Min=100/0)

Do you wish to continue (Y/N) - n

Answer 1

//Java code

package com.csc241;

public class Student

{

    private String fName ;

    private String lName ;

    private double[] grades;

    //Constructor
    public Student()
    {
        fName = "None";
        lName ="None";
        grades = null;
    }
    //Overload Constructor


    public Student(String fName, String lName, double[] grades) {
        this.fName = fName;
        this.lName = lName;
        this.grades = grades;
    }
    //getters and setters

    public String getfName() {
        return fName;
    }

    public void setfName(String fName) {
        this.fName = fName;
    }

    public String getlName() {
        return lName;
    }

    public void setlName(String lName) {
        this.lName = lName;
    }

    public double[] getGrades() {
        return grades;
    }

    public void setGrades(double[] grades) {
        this.grades = grades;
    }
    public double getAverage()
    {
        double sum =0;
        for (int i = 0; i <grades.length ; i++) {
            sum += grades[i];
        }
        double avg = sum/grades.length;
        return avg;
    }
    public double getMax()
    {
        double  max = grades[0];
        for (int i = 0; i <grades.length ; i++) {
            if(max<grades[i])
                max = grades[i];
        }
        return max;
    }
    public double getMin()
    {
        double  min = grades[0];
        for (int i = 0; i <grades.length ; i++) {
            if(min>grades[i])
                min = grades[i];
        }
        return min;
    }


    @Override
    public String toString() {
        return "Grade Statistics for "+fName+" "+lName+"(average = "+String.format("%.1f",getAverage())+"; max/min = "+String.format("%.0f",getMax())+"/"+String.format("%.0f",getMin())+")";
    }

}

//==================================

import com.csc241.Student;

import java.util.Scanner;

public class Main {
    public static void main(String[] args)
    {
        //Create student object
        Student student = new Student();
        //For user input
        Scanner input = new Scanner(System.in);

        Student[] students;
        System.out.print("How many students are in your class: ");
        int numberOfStudents = input.nextInt();
        students = new Student[numberOfStudents];

        for (int i = 0; i <students.length ; i++) {
            System.out.print("Enter the first name of student #"+(i+1)+": ");
            student.setfName(input.next());
            System.out.print("Enter "+student.getfName()+"'s last name: ");
            student.setlName(input.next());
            System.out.print("How many grades will you be entering for "+student.getfName()+" "+student.getlName()+"? ");
            int gradeSize = input.nextInt();
            double[] grades = new double[gradeSize];
            System.out.print("Plz enter the grades for "+student.getfName()+" "+student.getlName()+"\n");
            for (int j = 0; j <grades.length ; j++) {
                grades[j] = input.nextDouble();
            }
            student.setGrades(grades);
            students[i] = student;
            System.out.println(students[i]);
        }
    }
}

//Output

//If you need any help regarding this solution .......... please leave a comment ...... thanks