Element Modification in Multi-Dimensional Arrays in Java

Question

I have created a 2-D array in Java and I wish to change the value of each element.

Here is what I am trying to accomplish

-number each student from 1-10

-give each student 5 random marks from 40-100

int[][] students = new int[10][5];
Random numGen = new Random();

for (int i=0; i < students.length; i++){
    students[i] = i;         //Problem here..        
    for (int j=0; j<5; j++){
        students[i][j] = numGen.nextInt(40)+61
    }
}

I am having issues assigning each student a number from 1-10.

Where I wrote '//Problem here', is where the compiler keeps giving me trouble.

What is the appropriate method for modifying a single element in multi-dimension arrays?

Answer 1

Just use the index into the students (and return id as index+1 when you need to).

int[][] students = new int[10][5];
Random numGen = new Random();

for (int i=0; i < students.length; i++){     
    for (int j=0; j<5; j++){
        students[i][j] = numGen.nextInt(40)+61
    }
}

Answer 2

Array indices in java starts from 0 . Which means 1st row is represented as 0. To edit an element in a 2D array you need to specify the both indices. For example to edit an element at 5th row and 4th column you should use myArray[4][3] . Because you start counting from 0. myArray[0][0] is first element of the first row.

int[][] students = new int[10][5];
Random numGen = new Random();

for (int i=0; i < students.length; i++){
    students[i][0] = i; //Change student[i] = i to student[i] = i+i
                        // because i starts  from 0 but student number starts from 1.       
    for (int j=0; j<5; j++){
        students[i][j] = numGen.nextInt(40)+61
    }
}