Grade Book A Teacher has five students who have taken four tests. The teacher us
ID: 3622403 • Letter: G
Question
Grade Book
A Teacher has five students who have taken four tests. The teacher uses the following grading scale to assign a letter grade to a student, based on the average of his or her four test scores:
Test Score Letter Grade
90-100 A
80-89 B
70-79 C
60-69 D
0-59 E
Write a class that uses a String array or ArrayList object to hold the five students' names, an array of five characters to hold the five students' letter grades, and five arrays of four doubles each to hold each student's set of test scores. THe class should have methods that return a specific student's name, average test score, and a letter grade based on the average.
Demonstrate the class in a program that allows the user to enter each student's name and his/her four test scores. It should then display each student's average test score and letter grade.
INPUT VALIDATION: DO NOT ACCEPT TEST SCORES LESS THAN ZERO OR GREATER THAN 100.
public class GradeBook
{
// Constant for the number of students
private final int NUM_STUDENTS = 5;
// Constant for the number of tests
private final int NUM_TESTS = 4;
// Array to hold student names
private String[] names = new String[NUM_STUDENTS];
// Array to hold student grades
private char[] grades = new char[NUM_STUDENTS];
// Create arrays of scores, one for each student.
private double[] scores1 = new double[NUM_TESTS];
private double[] scores2 = new double[NUM_TESTS];
private double[] scores3 = new double[NUM_TESTS];
private double[] scores4 = new double[NUM_TESTS];
private double[] scores5 = new double[NUM_TESTS];
/**
The setName method assigns a student's name.
@param studentNumber The student's number.
@param name The student's name.
*/
public void setName(int studentNumber, String name)
{
// your code
}
/**
The setScores method copies an array of test scores
to a student's array of scores.
@param studentNumber The student's number.
@param scores An array of test scores.
*/
public void setScores(int studentNumber, double[] scores)
{
//your code
}
/**
The getName method returns a student's name.
@param studentNumber The specified student's number.
@return The student's name.
*/
public String getName(int studentNumber)
{
//your code
}
/**
The getAverage method returns a student's average
test score.
@param studentNumber The specified student's number.
@return The student's average test score.
*/
public double getAverage(int studentNumber)
{
//your code
}
/**
The getLetterGrade method returns a student's
letter grade.
@param studentNumber The specified student's number.
@return The student's letter grade.
*/
public char getLetterGrade(int studentNumber)
{
//your code
}
/**
copyArray is a private method that copies the contents
of one array to another.
@param to The array to copy to.
@param from The array to copy from.
*/
private void copyArray(double[] to, double[] from)
{
//your code
}
/**
calcAverage is a private method that calculates
the average of the values in an array of test scores.
@param scores The array with the test scores.
*/
private double calcAverage(double[] scores)
{
//your code
}
/**
assignGrade is a private method that determines and
assigns a letter grade to a specific student.
@param studentNumber The specified student's number.
*/
private void assignGrade(int studentNumber)
{
//your code
}
/**
determineGrade is a private method that determines
a letter grade for a test average.
@param average The test average.
@return The letter grade.
*/
private char determineGrade(double average)
{
//your code
}
}
Explanation / Answer
// save as GradeBook.java and run
public class GradeBook
{
// Constant for the number of students
private final int NUM_STUDENTS = 5;
// Constant for the number of tests
private final int NUM_TESTS = 4;
// Array to hold student names
private String[] names = new String[NUM_STUDENTS];
// Array to hold student grades
private char[] grades = new char[NUM_STUDENTS];
// Create arrays of scores, one for each student.
private double[] scores1 = new double[NUM_TESTS];
private double[] scores2 = new double[NUM_TESTS];
private double[] scores3 = new double[NUM_TESTS];
private double[] scores4 = new double[NUM_TESTS];
private double[] scores5 = new double[NUM_TESTS];
/**
The setName method assigns a student's name.
@param studentNumber The student's number.
@param name The student's name.
*/
public void setName(int studentNumber, String name)
{
names[studentNumber-1] = name;
}
/**
The setScores method copies an array of test scores
to a student's array of scores.
@param studentNumber The student's number.
@param scores An array of test scores.
*/
public void setScores(int studentNumber, double[] scores)
{
switch(studentNumber)
{
case 1:copyArray(scores1,scores); break;
case 2:copyArray(scores2,scores); break;
case 3:copyArray(scores3,scores); break;
case 4:copyArray(scores4,scores); break;
case 5:copyArray(scores5,scores); break;
default:break;
}
}
/**
The getName method returns a student's name.
@param studentNumber The specified student's number.
@return The student's name.
*/
public String getName(int studentNumber)
{
//your code
return names[studentNumber-1];
}
/**
The getAverage method returns a student's average
test score.
@param studentNumber The specified student's number.
@return The student's average test score.
*/
public double getAverage(int studentNumber)
{
//your code
double avg=0.0;
switch(studentNumber)
{
case 1:avg = calcAverage(scores1); break;
case 2:avg = calcAverage(scores2); break;
case 3:avg = calcAverage(scores3); break;
case 4:avg = calcAverage(scores4); break;
case 5:avg = calcAverage(scores5); break;
default:break;
}
return avg;
}
/**
The getLetterGrade method returns a student's
letter grade.
@param studentNumber The specified student's number.
@return The student's letter grade.
*/
public char getLetterGrade(int studentNumber)
{
char lettergrade; //your code
if(getAverage(studentNumber)>=90 && getAverage(studentNumber)<=100)
lettergrade = 'A';
else if(getAverage(studentNumber)>=80 && getAverage(studentNumber)<=89)
lettergrade = 'B';
else if(getAverage(studentNumber)>=70 && getAverage(studentNumber)<=79)
lettergrade = 'C';
else if(getAverage(studentNumber)>=60 && getAverage(studentNumber)<=69)
lettergrade = 'D';
else
lettergrade = 'E';
return lettergrade;
}
/**
copyArray is a private method that copies the contents
of one array to another.
@param to The array to copy to.
@param from The array to copy from.
*/
private void copyArray(double[] to, double[] from)
{
//your code
System.arraycopy(from, 0, to, 0, from.length);
}
/**
calcAverage is a private method that calculates
the average of the values in an array of test scores.
@param scores The array with the test scores.
*/
private double calcAverage(double[] scores)
{
//your code
double sum=0;
for(int i=0; i<scores.length; i++)
sum+=scores[i];
return sum/scores.length;
}
/**
assignGrade is a private method that determines and
assigns a letter grade to a specific student.
@param studentNumber The specified student's number.
*/
private void assignGrade(int studentNumber)
{
//your code
grades[studentNumber-1] = getLetterGrade(studentNumber);
}
/**
determineGrade is a private method that determines
a letter grade for a test average.
@param average The test average.
@return The letter grade.
*/
private char determineGrade(double average)
{
//your code
char lettergrade; //your code
if(average>=90 && average<=100)
lettergrade = 'A';
else if(average>=80 && average<=89)
lettergrade = 'B';
else if(average>=70 && average<=79)
lettergrade = 'C';
else if(average>=60 && average<=69)
lettergrade = 'D';
else
lettergrade = 'E';
return lettergrade;
}
public static void main(String[] args)
{
GradeBook GB = new GradeBook();
GB.setName(1, "Aswani");
GB.setName(2,"Kumar");
GB.setName(3, "Ravi");
GB.setName(4, "Karuna");
GB.setName(5,"Savita");
double[] scores1 = {97,98,96,98};
GB.setScores(1, scores1);
double[] scores2 = {87,88,86,88};
GB.setScores(2, scores2);
double[] scores3 = {77,76,79,78};
GB.setScores(3, scores3);
double[] scores4 = {68,68,66,68};
GB.setScores(4, scores4);
double[] scores5 = {58,58,56,58};
GB.setScores(5, scores5);
for(int i=1; i<6; i++)
{
System.out.println(GB.getName(i) + " Has got Average "+ GB.getAverage(i) + " and Grade is " + GB.determineGrade(GB.getAverage(i)) );
}
}
}
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