Question

Your assignment is to write a grade book for a teacher. The teacher has a text file, which includes student's names, and students test grades. There are four test scores for each student. Here is an example of such a file:

Count: 5
Sally 78.0 84.0 79.0 86.0
Rachel 68.0 76.0 87.0 76.0
Melba 87.0 78.0 98.0 88.0
Grace 76.0 67.0 89.0 0.0
Lisa 68.0 76.0 65.0 87.0

The first line of the file will indicate the number of students in the class. Each sub sequence line will list the student's first name, followed by their four exam scores (all separated by spaces).

The overall average for each student will be calculated by averaging the three highest test scores for each student. The teacher uses the following grading scale to assign a letter grade to a student:

• 90 to 100 is an A
• 80 to 89 is a B
• 70 to 79 is a C
• 60 to 69 is a D
• 59 and lower is E

  Write a class called GradeBook that uses the following instance variables (attributes):

• A public constant, NUM_TESTS that contains the number of test scores.
• A private int, numStudents that stores the number of students in the grade book.
• An array of Strings to hold names of students. It will be sized based on the number of students in the file
• An array of characters to hold the final letter grade of each student. It will be the same size as array above.
• A two-dimensional array of type double consisting of test scores for each student. It is of size number of students by NUM_TESTS (there are 4 tests). The number of students in the file might vary. You should check the first line in the file to get the count of the number of students so that you can instantiate Arrays of the appropriate size.
  Method Description This constructor method will: Open the file who's name is passed in as a String . Instantiate the names, letter qrades, and test scores arrayS . read in all of the student data from the file and store it in the appropriate arrays public GradeBook(String fileName) Lastly, this constructor will call the assignGrades method to compute and assign the letter grade for each student. Since this method is doing IO operation you should specify that this method may throw and IO exception; For example throws IOException A helper method that calculates the average of the three highest exam scores; returns an average score if the parameter is a valid index number. Return -1 otherwise private double getStudentAverage (int index) A helper method that calls getStudentAverage to calculate the average score for each student and assigns a letter grade as follows: A 90-100 B 80-89 С 70-79 D 60-69 E 0-59 Returns the student name if the parameter is a valid index number; return null otherwise Returns the letter grade of the student that corresponds to the parameter index if the parameter is a valid index number. Returns a blank space otherwise Returns the index of the student whose name matches the parameter target; returns -1 if the target name is not found Returns a String, which contains students' names averages, and the final letter grades for each student in the array. (Please see the sample output) private void assignGrades0 public String getStudentName (int index) public char getLetterGrade (int index) public int getlndex(String studentName) public String toString0
  

• Note: You may add more methods to the class if it you wish.

  After implementing the GradeBook class, use the given Assgnment8.java. which has the main method to test your class. The program asks the user for the file name.

• Assgnment8.java

import java.util.Scanner;
import java.io.*;

public class Assignment8
{
static Scanner in = new Scanner(System.in);

public static void main (String[] args) throws IOException
{
String command = " ";
System.out.print("Please enter the filename: ");
String fileName = in.nextLine();

GradeBook grades = new GradeBook(fileName);

while (command.charAt(0) != 'q') {   
System.out.println();
System.out.print("Please enter a command or type \"?\" to see the menu: ");
command = in.nextLine();

switch (command.charAt(0)) {
case 'a': // display all
System.out.println(grades.toString());
break;
case 'b' : // search
System.out.print("Type student name: ");
String name = in.nextLine();
int index = grades.getIndex(name);
char grade = grades.getLetterGrade(index);
if (index != -1)
System.out.println(name + " " + grade);
else
System.out.println("Student doesn't exist!");
break;

case '?' : // help menu
System.out.println("a: Display ");
System.out.println("b: Search ");
System.out.println("?: Help menu ");
System.out.println("q: Stop the program ");
break;

case 'q': // stop the program
break;

default:
System.out.println("Illegal cammand!!!");
} // end of switch
} // end of while
}// end main
} // end Assignment8

Helpful hints for doing this assignment:

• Work on it in steps – write one method, test it with a test driver and make sure it works before going on to the next method
• Always make sure your code compiles before you add another method

Sample Output: with user input in red

Please enter the filename: roster.txt

Please enter a command or type "?" to see the menu: a
Sally         83.0  B
Rachel        79.7  C
Melba         91.0  A
Grace         77.3  C
Lisa          77.0  C

Please enter a command or type "?" to see the menu: b
Type student name: Melba
Melba A

Please enter a command or type "?" to see the menu: b
Type student name: Lisa
Lisa C

Please enter a command or type "?" to see the menu: b
Type student name: Rick
Student doesn't exist!

Please enter a command or type "?" to see the menu: q

Note: Do not use any Java language or library features that we have not already covered in class. For example, do not use ArrayLists.

Answer 1

If you have any doubts, please give me comment...

import java.util.Scanner;

import java.io.*;

public class GradeBook{

public static final int NUM_TESTS = 4;

private int numStudents;

private String[] names;

private char[] grades;

private double scores[][];

public GradeBook(String fileName) throws IOException{

Scanner fin = new Scanner(new File(fileName));

int n=0;

fin.next(); //skipping count string

numStudents = fin.nextInt();

names = new String[numStudents];

grades = new char[numStudents];

scores = new double[numStudents][NUM_TESTS];

while(fin.hasNext()){

names[n] = fin.next();

for(int i=0; i<NUM_TESTS; i++)

scores[n][i] = fin.nextDouble();

n++;

}

assignGrades();

fin.close();

}

private double getStudentAverage(int index){

double sum = 0.0;

for(int i=0; i<NUM_TESTS;i++){

sum += scores[index][i];

}

return sum/NUM_TESTS;

}

private void assignGrades(){

for(int i=0; i<numStudents; i++){

double avg = getStudentAverage(i);

if(avg>=90 && avg<=100)

grades[i] = 'A';

else if(avg>=80 && avg<90)

grades[i] = 'B';

else if(avg>=70 && avg<80)

grades[i] = 'C';

else if(avg>=60 && avg<70)

grades[i] = 'D';

else

grades[i] = 'E';

}

}

public String getStudentName(int index){

return names[index];

}

public char getLetterGrade(int index){

return grades[index];

}

public int getIndex(String studentName){

for(int i=0; i<numStudents; i++){

if(names[i].equalsIgnoreCase(studentName))

return i;

}

return -1;

}

public String toString(){

String str = "";

for(int i=0; i<numStudents; i++){

str += names[i]+"\t"+getStudentAverage(i)+"\t"+grades[i]+"\n";

}

return str;

}

}

import java.util.Scanner;

import java.io.*;

public class Assignment8 {

static Scanner in = new Scanner(System.in);

public static void main(String[] args) throws IOException {

String command = " ";

System.out.print("Please enter the filename: ");

String fileName = in.nextLine();

GradeBook grades = new GradeBook(fileName);

while (command.charAt(0) != 'q') {

System.out.println();

System.out.print("Please enter a command or type \"?\" to see the menu: ");

command = in.nextLine();

switch (command.charAt(0)) {

case 'a': // display all

System.out.println(grades.toString());

break;

case 'b': // search

System.out.print("Type student name: ");

String name = in.nextLine();

int index = grades.getIndex(name);

char grade = grades.getLetterGrade(index);

if (index != -1)

System.out.println(name + " " + grade);

else

System.out.println("Student doesn't exist!");

break;

case '?': // help menu

System.out.println("a: Display ");

System.out.println("b: Search ");

System.out.println("?: Help menu ");

System.out.println("q: Stop the program ");

break;

case 'q': // stop the program

break;

default:

System.out.println("Illegal cammand!!!");

} // end of switch

} // end of while

}// end main

} // end Assignment8