Issue with two dimensional arrays

[Tiberius Marius]

I have the program bellow that grades students(based on a two dimensional array with the answers) and i need to make it display the students based on the grades/scores in ascending order . I did that in two ways (using a array and a two dimensional array) but i have a hunch it can be done much more simple then i did it (but still using array object and nothing else ) . Any input about how to solve the problem in a more easy way is appreciated !

public class GradeExam {
  /** Main method */
  public static void main(String args[]) {
    // Students' answers to the questions
    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'}};

    // Key to the questions
    char[] keys = {'D', 'B', 'D', 'C', 'C', 'D', 'A', 'E', 'A', 'D'};

    // Grade all answers
    for (int i = 0; i < answers.length; i++) {
      // Grade one student
      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);
    }
  }
}

My first solution creating an array with the grades for sorting :

public class C8_3 {
    public static void main(String args[]) {
        // Students' answers to the questions
        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'}};

        // Key to the questions
        char[] keys = {'D', 'B', 'D', 'C', 'C', 'D', 'A', 'E', 'A', 'D'};
        
        
        //int[][] grades = new int[answers.length][2];
        int[] grades = new int[answers.length];
        
        // Grade all answers
        for (int i = 0; i < answers.length; i++) {
          // Grade one student
            int correctCount = 0;
            for (int j = 0; j < answers[i].length; j++) {
                if (answers[i][j] == keys[j])
                correctCount++;
            }
            grades[i] = correctCount  ;  
         
        }
        orderGrades(grades);
        
      
    }
    
   
    
    public static int maxArray(int[] a){
        int max;
        
        
        
       
        max = a[0];
        for(int j =0 ; j < a.length ; j++){
            if(max < a[j]){
                max = a[j];
                    
            }
        }
        return max;
    }
    
    
    public static void orderGrades(int[]a){
        int max =maxArray(a);
        int min ;
        int index = 0 ;
        
        
        for(int i = 0 ; i < a.length ; i++){
            min = a[0];
            index = 0;
            for(int j =0 ; j < a.length ; j++){
                if(min > a[j]){
                    min = a[j];
                    index =j ;
                }
            }
            System.out.println("Student " + index + "'s correct count is " +
            min);
            max++;
            a[index]= max ;
            
        }
    }
    
    
}
    

My second solution using a two dimensional array :

public class C8_3v2 {
    public static void main(String args[]) {
        // Students' answers to the questions
        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'}};

        // Key to the questions
        char[] keys = {'D', 'B', 'D', 'C', 'C', 'D', 'A', 'E', 'A', 'D'};
        
        
        int[][] grades = new int[answers.length][2];
        
        
        // Grade all answers
        
        for (int i = 0; i < answers.length; i++) {
          // Grade one student
            int correctCount = 0;
            for (int j = 0; j < answers[i].length; j++) {
                if (answers[i][j] == keys[j])
                correctCount++;
            }
              
            grades[i][0]= i;
            grades[i][1] = correctCount;
        }
        
        for(int i = 0 ; i < grades.length ;i++){
            //System.out.println("student"+grades[i][0]+" with grade "+grades[i][1]);
        }
        orderGrades(grades);
        for(int i = 0 ; i < grades.length ;i++){
            System.out.println("Student " + grades[i][0] + "'s correct count is " +grades[i][1]);
        }
        
    }
    
    
    
   
    
 
    
    public static void orderGrades(int[][] a){
        int min ;
        int index ;
        int temp1 ;
        int temp2 ;
        
        for(int r = 0 ; r < a.length ; r++){
            index = r;
            min = a[r][1];
            for(int j = r ; j < a.length ;j++){
                if( min > a[j][1]){
                min = a[j][1];
                index =j ;
                }
            }
            temp1 = a[r][0];
            temp2 = a[r][1];
            a[r][0] = a[index][0];
            a[r][1] = a[index][1];
            a[index][0] = temp1;
            a[index][1] = temp2;
            
            
        }
    }
}

[fred rosenberger]

I only see one-dimensional arrays here. That's because Java only supports one-dimensional arrays, but they can hold...arrays.

In other words, you have an array that holds a bunch of character arrays.

[Tiberius Marius]

Well , in the book that i m learning Java from i have a whole chapter called Multidimensional Arrays.

[Campbell Ritchie]

In which case the book is wrong, or at least misleading.
Start by writing yourself a utility class for arrays. I'll give you a start. Private constructor because you never need any instances of it. All methods static.

public class MrrayUtils
{
   private ArrayUtils()
   {
      // empty constructor, never called.
   }

   public void swapTwoElementsInArray(int[] arr, int i, int j)
   {
      // real code goes here.
   }

   public void sortArray(int[] arra)
   {
      // real code goes here.
   }
// other methods
}

Always use the methods of that class; never put sorting logic in other methods. If the methods you have already work you can simply copy them into the utility class.