Thread: Problems getting value of index in 2D array operation

Before starting to tell the problem with my method, I want to greet everyone in Java community

This time, I have a problem with an 2D array.
Arr is of integer type with dimensions of [4][4].
Let me display the code...

...
public static void main(String args[]) {
  int[][]arr = new int[4][4];
    int size=0;
for (int i = 0; i < size; i++) {
    for (int j = 0; j < size; j++) {
        arr[i][j] = size * j + i;
IO.outputln("result is: "+arr[i]+arr[j]);
    }
}
}

I would like to know the value stored in arr[1][3] after executing the code above.
I can't see the value in the console. What is missing ?

What result are you getting? Copy and post the console from a sample run.

You've used the 'size' variable before (I think), and you shouldn't be. That's what you're missing in this case. Post your corrected code, and then I'll show you a better way.

Hi Greg.
I can't tell you the result of the operation, because the terminal window doesn't show me anything.
About the variable size, I don't know. I just copied this small line of code from my teacher example to create a better understanding program with an output result ^^

That you're seeing nothing in the terminal window is the result, and it's significant.

Trace the code - keep track of the variable values with pencil and paper if you need to - and determine what will happen at the for loops with size set to 0.

Glad you figured it out. As I said earlier, the code below demonstrates a more appropriate way to write for() loops to iterate arrays.

// a method to demonstrate the declaration and initialization
// of a 2D array with 4 rows and 4 columns. the first element of
// each row of the array is initialized to the row number, and
// each element in the row thereafter increases by one
public static void arrayMethod()
{
    // declare a 2D array with 4 rows and 4 columns
    int[][] arr = new int[4][4];
 
    // initialize the array
    // for each row, i: arr.length = number of rows
    for (int i = 0 ; i < arr.length ; i++)
    {
        // for each column, j: arr[i].length = the number of
        // elements or columns in the row i
        for (int j = 0 ; j < arr[i].length ; j++)
        {
            arr[i][j] = j + i;
        }
    }
 
    // display the completed array
    System.out.println( Arrays.deepToString( arr ) );
 
} // end method arrayMethod()