Thread: Two-Dimensional Array to Grade Students?

I'm a bit stuck with a homework assignment.

Here is my working code...

   import java.util.Scanner;
   public class GradeExam {
      public static void main(String[] args) {
         char[][] answers = {
               {'A', 'B', 'A', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'D', 'B', 'A', 'B', 'C', 'A', 'E', 'E', 'A', 'D'},
               {'E', 'D', 'D', 'A', 'C', 'B', 'E', 'E', 'A', 'D'},
               {'C', 'B', 'A', 'E', 'D', 'C', 'E', 'E', 'A', 'D'},
               {'A', 'B', 'D', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'B', 'B', 'E', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'B', 'B', 'A', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'E', 'B', 'E', 'C', 'C', 'D', 'E', 'E', 'A', 'D'}}; 	
 
         char[] keys = {'D', 'B', 'D', 'C', 'C', 'D', 'A', 'E', 'A', 'D'};
 
         for (int i = 0; i < answers.length; i++) {
 
            int correctCount = 0;
            for (int j = 0; j < answers[i].length; j++) {
               if (answers[i][j] == keys[j])
                  correctCount++;     
            } 
            System.out.println("Student " + i + "'s correct count is " + correctCount);
         }
      }
   }

Well my teacher wants some "tweaks" made to the program that I'm having trouble figuring out.

He wants me to display the students in increasing order of the numbers of correct answers. He also wants the grade inputs echoed before the return.

Can someone give me a hand with this?

What do you mean by "grade inputs echoed before the return"?

main is void. It doesn't have a return(unless you'd like to call one like
return;
, which will basically be the same thing as System.exit(0); in this case).

I'm assuming you mean the println().

I did so far find a way to figure out how to keep your correct count for each student even after your for loops end.

I'm not that good at sorting things but might be able to think of more when it's not 2:00 a.m..

I have this so far:

	import java.util.*;
 
	public class Student
	{
 
	private int correctCount;
 
	public Student (int correctCount)
	{
	 setCorrectCount(correctCount);
	}
 
	public void setCorrectCount(int correctCount)
	{
	this.correctCount = correctCount;
	}
 
	public int getCorrectCount()
	{
	return correctCount;
	}
	}

 import java.util.Scanner;
   public class GradeExam {
 
 
 
	static Student[] students;
      public static void main(String[] args) {
         char[][] answers = {
               {'A', 'B', 'A', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'D', 'B', 'A', 'B', 'C', 'A', 'E', 'E', 'A', 'D'},
               {'E', 'D', 'D', 'A', 'C', 'B', 'E', 'E', 'A', 'D'},
               {'C', 'B', 'A', 'E', 'D', 'C', 'E', 'E', 'A', 'D'},
               {'A', 'B', 'D', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'B', 'B', 'E', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'B', 'B', 'A', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'E', 'B', 'E', 'C', 'C', 'D', 'E', 'E', 'A', 'D'}}; 	
 
         char[] keys = {'D', 'B', 'D', 'C', 'C', 'D', 'A', 'E', 'A', 'D'};
          students = new Student[answers.length];
 
			for (int k =0; k < students.length; k++)
			{
			students[k] = new Student(0);
			}
 
 
 
         for (int i = 0; i < answers.length; i++) {
 
            int correctCount = 0;
 
            for (int j = 0; j < answers[i].length; j++) {
               if (answers[i][j] == keys[j])
                  correctCount++;     
						students[i].setCorrectCount(correctCount);
            } 
            System.out.println("Student " + i + "'s correct count is " + correctCount);
         }
 
			for (int v =0; v < students.length; v++)
			{
			System.out.println(students[v].getCorrectCount());
			}
      }
   }

Originally Posted by Console

Student 0's correct count is 7
Student 1's correct count is 6
Student 2's correct count is 5
Student 3's correct count is 4
Student 4's correct count is 8
Student 5's correct count is 7
Student 6's correct count is 7
Student 7's correct count is 7
7
6
5
4
8
7
7
7

Not sure what your code did to keep up with the count. The program already kept up with that.

I did however solve the "echoing" the input of the students grades before the results...

   import java.util.Scanner;
   public class GradeExam {
      public static void main(String[] args) {
         char[][] answers = {
               {'A', 'B', 'A', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'D', 'B', 'A', 'B', 'C', 'A', 'E', 'E', 'A', 'D'},
               {'E', 'D', 'D', 'A', 'C', 'B', 'E', 'E', 'A', 'D'},
               {'C', 'B', 'A', 'E', 'D', 'C', 'E', 'E', 'A', 'D'},
               {'A', 'B', 'D', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'B', 'B', 'E', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'B', 'B', 'A', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'E', 'B', 'E', 'C', 'C', 'D', 'E', 'E', 'A', 'D'}}; 	
 
         char[] keys = {'D', 'B', 'D', 'C', 'C', 'D', 'A', 'E', 'A', 'D'};
 
 
         for (int i = 0; i < answers.length; i++) {
 
            int correctCount = 0;
            for (int j = 0; j < answers[i].length; j++) {
               System.out.println(answers[i][j]);
               if (answers[i][j] == keys[j])
                  correctCount++;            		    
            }          
            System.out.println("Student " + i + "'s correct count is " + correctCount);
         }
      }
   }

My problem now is just the sorting problem. For some reason I feel I need to use a selection sort or something on the correctCount?

Not sure how to pull that off yet. Any ideas?

Originally Posted by Java Neil

Not sure what your code did to keep up with the count. The program already kept up with that.

I did however solve the "echoing" the input of the students grades before the results...

   import java.util.Scanner;
   public class GradeExam {
      public static void main(String[] args) {
         char[][] answers = {
               {'A', 'B', 'A', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'D', 'B', 'A', 'B', 'C', 'A', 'E', 'E', 'A', 'D'},
               {'E', 'D', 'D', 'A', 'C', 'B', 'E', 'E', 'A', 'D'},
               {'C', 'B', 'A', 'E', 'D', 'C', 'E', 'E', 'A', 'D'},
               {'A', 'B', 'D', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'B', 'B', 'E', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'B', 'B', 'A', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'E', 'B', 'E', 'C', 'C', 'D', 'E', 'E', 'A', 'D'}}; 	
 
         char[] keys = {'D', 'B', 'D', 'C', 'C', 'D', 'A', 'E', 'A', 'D'};
 
 
         for (int i = 0; i < answers.length; i++) {
 
            int correctCount = 0;
            for (int j = 0; j < answers[i].length; j++) {
               System.out.println(answers[i][j]);
               if (answers[i][j] == keys[j])
                  correctCount++;            		    
            }          
            System.out.println("Student " + i + "'s correct count is " + correctCount);
         }
      }
   }

My problem now is just the sorting problem. For some reason I feel I need to use a selection sort or something on the correctCount?

Not sure how to pull that off yet. Any ideas?

I've been working on this one a while as you can see, and I'm still stuck. Once again, I need to figure out how to "sort" the students and their grades before the display. Can someone give me a hand with this?

Neil

Well I have made some progress. My teacher requires everything that can be done in JOptionPane to be so.

Here is the updated code...

   import javax.swing.JOptionPane;
   public class GradeExam {
      public static void main(String[] args) {
         char[][] answers = {
               {'A', 'B', 'A', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'D', 'B', 'A', 'B', 'C', 'A', 'E', 'E', 'A', 'D'},
               {'E', 'D', 'D', 'A', 'C', 'B', 'E', 'E', 'A', 'D'},
               {'C', 'B', 'A', 'E', 'D', 'C', 'E', 'E', 'A', 'D'},
               {'A', 'B', 'D', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'B', 'B', 'E', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'B', 'B', 'A', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'E', 'B', 'E', 'C', 'C', 'D', 'E', 'E', 'A', 'D'}}; 	
 
         char[] keys = {'D', 'B', 'D', 'C', 'C', 'D', 'A', 'E', 'A', 'D'};       
 
         for (int i = 0; i < answers.length; i++) {
            int correctCount = 0;
          //Convert input to a String
            String result = "Student " + i + "'s answers were \n";
            for (int j = 0; j < answers[i].length; j++) {
               result += answers[i][j] + " ";
               if (answers[i][j] == keys[j])
                  correctCount++;            		    
            }        
          //Display the input
            JOptionPane.showMessageDialog(null, result + "\nStudent " 
               + i + "'s correct count is " + correctCount);                 
         }
      }
   }

I still need some help on sorting everything based on the correct count of the grades. I've really tried everything I can think of and am at the point of pulling my hair out. Pleeeeeeese help! Even if it's just a tip on how to think of the logic.

I hate to be a needy person, but I really need some help here. This is due to turn in tomorrow!

Originally Posted by vanDarg

To enter the correctCount into the array:

sort[i] = correctCount

With this code, if 'i' was 2 and correctCount was 7, then student number 3 (remember, start at 0) would have 7 correct answers. Look at the previous code I displayed in a previous post to see where you enter this into your code. This should be entered after each inner loop has completed, and before you move onto the next student.

Wow...your grasp of java is amazing! My grasp...not so much.

I tried to apply what you said to no avail. It's not storing the correctCount? I've obviously missed something.

I used the new array student[i] = correctCount; When I used sort[i] = correctCount it just said the it couldn't find it.

Here is my latest code...

   import javax.swing.JOptionPane;
   public class GradeExam {
      public static void main(String[] args) {
         char[][] answers = {
               {'A', 'B', 'A', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'D', 'B', 'A', 'B', 'C', 'A', 'E', 'E', 'A', 'D'},
               {'E', 'D', 'D', 'A', 'C', 'B', 'E', 'E', 'A', 'D'},
               {'C', 'B', 'A', 'E', 'D', 'C', 'E', 'E', 'A', 'D'},
               {'A', 'B', 'D', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'B', 'B', 'E', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'B', 'B', 'A', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'E', 'B', 'E', 'C', 'C', 'D', 'E', 'E', 'A', 'D'}}; 	
 
         char[] keys = {'D', 'B', 'D', 'C', 'C', 'D', 'A', 'E', 'A', 'D'};       
         int[] student = new int[8];
       //Create new array to sort students 
         String studentSort = "The list of students in order: \n";
         for (int x = 0; x < 8; x++) {
            studentSort += student[x] + " \n";
         }
 
       //Echo the answers
         String result = "The answer key to the test: \n";
         for (int k = 0; k < 10; k++) {
            result += keys[k] + " ";
 
         }
         for (int i = 0; i < answers.length; i++) {
            int correctCount = 0;
          //Convert grades to a String
            String result2 = "Student " + i + "'s answers are: \n";
            for (int j = 0; j < answers[i].length; j++) {
               result2 += answers[i][j] + " ";
               if (answers[i][j] == keys[j])
                  correctCount++;
						student[i] = correctCount;           		    
            } 	
 
          //Display the input
            JOptionPane.showMessageDialog(null, result + "\n" + result2 + 
               "\nStudent " + i + "'s correct count is " + correctCount);                 
         }
 
         JOptionPane.showMessageDialog(null, studentSort);
      }
   }

Could you make some more notes with this code? I have the first display just as my teacher wants it, but if I have to change everything, so be it.

You the man!

Originally Posted by vanDarg

A quick word of advice, when writing code, there are many things that factor into the readability of your code. This includes but is not limited to: line indentation, the use of open space, the use of brackets, etc. See Java Coding Style Guide for more info

I bring this up because although it may be tempting to not use brackets with an if statement, it may reduce someone's ability to read it correctly. Also, make sure all lines are justified correctly, with your code, it almost looks like the line:
student[i] = correctCount;
is included in the if statement. Left justify to correct this, especially of you are asking people to read your code.

for (int i = 0; i < answers.length; i++) {
            int correctCount = 0;
          //Convert grades to a String
            String result2 = "Student " + i + "'s answers are: \n";
            for (int j = 0; j < answers[i].length; j++) {
               result2 += answers[i][j] + " ";
               if (answers[i][j] == keys[j])
                  correctCount++;
						student[i] = correctCount;           		    
            }

Moving forward, here are some notes

import javax.swing.JOptionPane;
   public class GradeExam {
      public static void main(String[] args) {
         char[][] answers = {
               {'A', 'B', 'A', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'D', 'B', 'A', 'B', 'C', 'A', 'E', 'E', 'A', 'D'},
               {'E', 'D', 'D', 'A', 'C', 'B', 'E', 'E', 'A', 'D'},
               {'C', 'B', 'A', 'E', 'D', 'C', 'E', 'E', 'A', 'D'},
               {'A', 'B', 'D', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'B', 'B', 'E', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'B', 'B', 'A', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'E', 'B', 'E', 'C', 'C', 'D', 'E', 'E', 'A', 'D'}}; 	
 
         char[] keys = {'D', 'B', 'D', 'C', 'C', 'D', 'A', 'E', 'A', 'D'};       
         int[] student = new int[8];
       //Create new array to sort students 
         String studentSort = "The list of students in order: \n";
         for (int x = 0; x < 8; x++) {                       // This block of code is out of place
            studentSort += student[x] + " \n";            // Move this String declaration and for loop to below
         }
 
       //Echo the answers
         String result = "The answer key to the test: \n";
         for (int k = 0; k < 10; k++) {
            result += keys[k] + " ";
 
         }
         for (int i = 0; i < answers.length; i++) {
            int correctCount = 0;
          //Convert grades to a String
            String result2 = "Student " + i + "'s answers are: \n";
            for (int j = 0; j < answers[i].length; j++) {
               result2 += answers[i][j] + " ";
               if (answers[i][j] == keys[j])
                  correctCount++;
						student[i] = correctCount;           		    
            } 	
 
          //Display the input
            JOptionPane.showMessageDialog(null, result + "\n" + result2 +        // Leave this code here to display
               "\nStudent " + i + "'s correct count is " + correctCount);                 
         }
        // Here you want to sort the array, I think I remember helping you with a bubble sort algorithm so this shouldn't be  too hard.
 
        // After the array is sorted, use the code from above if you'd like to enter the information into a string so that you 
       // Can output with JOptionPane
         JOptionPane.showMessageDialog(null, studentSort);
      }
   }

I'm not sure what your teacher wants as far as display, but as far as I can see you shouldn't have to re-write anything. Post back with more questions. At this point, helping you a step at a time is probably most beneficial so you don't feel overwhelmed.

First I want to apologize for the bad coding style. I have saved that PDF for a nice long read. I'm sure it's a pain for you pros to read script that is not well formatted.

Secondly as far as the code, I understand what needs to be done from your notes. My concern is as of now the code is not storing the input to be sorted i.e The student and their correctCount. Right now the last printout looks like...

The list of students in order:
0
0
0
0
0
0
0
0

Doesn't that mean I have nothing to sort?

Originally Posted by vanDarg

Oh don't worry about it, no big deal I just wanted to let you know.
And yes, all zeros would mean that you don't have to sort it. But we are obviously getting that in error. Thoroughly check your code, ensure that you are accessing the correct array when listing the students.

I thought you said that "student[i] = correctCount;" was the proper way to enter the correctCount into the array?

I promise I'm trying as hard as I can. I am no slacker. I'm just missing the point.

Originally Posted by vanDarg

It is the correct way, which is why I suspect that this line may be out of place, or that you are not accessing the correct array. Post your final code again, please

Sure thing

import javax.swing.JOptionPane;
   public class GradeExam {
      public static void main(String[] args) {
         char[][] answers = {
               {'A', 'B', 'A', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'D', 'B', 'A', 'B', 'C', 'A', 'E', 'E', 'A', 'D'},
               {'E', 'D', 'D', 'A', 'C', 'B', 'E', 'E', 'A', 'D'},
               {'C', 'B', 'A', 'E', 'D', 'C', 'E', 'E', 'A', 'D'},
               {'A', 'B', 'D', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'B', 'B', 'E', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'B', 'B', 'A', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'E', 'B', 'E', 'C', 'C', 'D', 'E', 'E', 'A', 'D'}}; 	
 
         char[] keys = {'D', 'B', 'D', 'C', 'C', 'D', 'A', 'E', 'A', 'D'};       
         int[] student = new int[8];
       //Create new array to sort students 
         String studentSort = "The list of students in order: \n" + "\n";
         for (int x = 0; x < 8; x++) {
            studentSort += student[x] + " \n";
         }
 
       //Echo the answers
         String result = "The answer key to the test: \n";
         for (int k = 0; k < 10; k++) {
            result += keys[k] + " ";
 
         }
         for (int i = 0; i < answers.length; i++) {
            int correctCount = 0;
          //Convert grades to a String
            String result2 = "Student " + i + "'s answers are: \n";
            for (int j = 0; j < answers[i].length; j++) {
               result2 += answers[i][j] + " ";
               if (answers[i][j] == keys[j])
                  correctCount++;
						student[i] = correctCount;           		    
            } 	
 
          //Display the input
            JOptionPane.showMessageDialog(null, result + "\n" + result2 +        // Leave this code here to display
               "\nStudent " + i + "'s correct count is " + correctCount);                 
         }
        // Here you want to sort the array, I think I remember helping you with a bubble sort algorithm so this shouldn't be  too hard.
         JOptionPane.showMessageDialog(null, studentSort);
      }
   }

You have the patience of a good teacher!

OK...I've actually made some progress

   import javax.swing.JOptionPane;
   public class Pract {
      public static void main(String[] args) {
         char[][] answers = {
               {'A', 'B', 'A', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'D', 'B', 'A', 'B', 'C', 'A', 'E', 'E', 'A', 'D'},
               {'E', 'D', 'D', 'A', 'C', 'B', 'E', 'E', 'A', 'D'},
               {'C', 'B', 'A', 'E', 'D', 'C', 'E', 'E', 'A', 'D'},
               {'A', 'B', 'D', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'B', 'B', 'E', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'B', 'B', 'A', 'C', 'C', 'D', 'E', 'E', 'A', 'D'},
               {'E', 'B', 'E', 'C', 'C', 'D', 'E', 'E', 'A', 'D'}}; 	
 
         char[] keys = {'D', 'B', 'D', 'C', 'C', 'D', 'A', 'E', 'A', 'D'};       
       //Create new array to sort students
         int[] student = new int[8];
 
       //Echo the answers
         String result = "The answer key to the test: \n";
         for (int k = 0; k < 10; k++) {
            result += keys[k] + " ";
 
         }
         for (int i = 0; i < answers.length; i++) {
            int correctCount = 0;
          //Convert grades to a String
            String result2 = "Student " + (i + 1) + "'s answers are: \n";
            for (int j = 0; j < answers[i].length; j++) {
               result2 += answers[i][j] + " ";
               if (answers[i][j] == keys[j])
                  correctCount++;
               student[i] = correctCount;           		    
            } 	
 
          //Display the input
            JOptionPane.showMessageDialog(null, result + "\n" + result2 +        
               "\nStudent " + (i + 1) + "'s correct count is " + correctCount);                 
         }               
           //Find the maximum in the list
         for (int i = student.length - 1; i > 0; i--) {          
            int currentMax = student[i];
            int currentMaxIndex = i;          
 
            for (int j = i - 1; j > (-1); j--) {
               if (currentMax < student[j]) {
                  currentMax = student[j];
                  currentMaxIndex = j;
               }
            }
 
             //Swap student[i] with list[currentMinIndex] if necessary
            if (currentMaxIndex != i) {
               student[currentMaxIndex] = student[i];
               student[i] = currentMax;
 
             //Convert input to a String
               String result3 = "Students scores \n";
               for (i = 0; i < student.length; i++) {
                  result3 += student[i] + " \n";
               }
 
             //Display the input
               JOptionPane.showMessageDialog(null, result3);  
            }
         }
      }
   }

The program now saves the correctCount and sorts it. Thanks!

My only problems are there is no student associated with the scores and the the sorting takes a few iterations to actually sort.

What am I overlooking?

OK...let me mess with this logic

Originally Posted by vanDarg

Good work.
First, you CAN associate a student with the score, since the array at position 0 would represent student 1, and position 1 would represent student 2, and so on:

String result3 = "Students scores \n";
               for (i = 0; i < student.length; i++) {
                  result3 += "Student number " + i + "score: " + student[i] + " \n";

Just add 1 to i
Second, you are entering the information into a string within an if statement, place it outside of that statement, as well as outside of the loop doing the sorting. Entering this information into a string should come after the sorting has completed.

Well I am not seeing the students switch with the correctCount. The students are not being sorted.

Should I use

int[][] student = new int[8][8];

to store the two values?

Also I'm not seeing what you mean with the if statements.