I am not able to understand the output generated in addition of 2D arrays ...particularly showing matrix addition

Hi Shinia, Run this. I have written some comments. If you could not understand anything, Please let me know:

package com.programming.module7;

public class MultiDimensionalArrays {
	public static void main(String[] args) {
		
		// 2D
		int[][] intArr = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
		for (int i = 0; i < intArr.length; i++) {
			for (int j = 0; j < intArr.length; j++) {
				//individually printing row and column of each array index 
				System.out.print(intArr[i][j] + " ");
			}
			//next line
			System.out.println();
		}
		
		System.out.println();
		
		int[][] a = {{1, 2, 3}, {4, 5, 6}};
		int[][] b = {{1, 2, 3}, {4, 5, 6}};
		
		//another matrix to store the sum of two matrices    
		int[][] c = new int[2][3];
		
		//adding and printing addition of 2 matrices    
		for (int i = 0; i < 2; i++) {
			for (int j = 0; j < 3; j++) {
				// for example c[0][0] is a[0][0] + b[0][0] which is 2
				// then a[0][1] + b[0][1] which is 4, so on and so forth
				c[i][j] = a[i][j] + b[i][j];
				System.out.print(c[i][j] + " ");
			}
			System.out.println();
		}
		System.out.println();
	}
}

why does it show exception:Index 3 out of bounds for length 3

and how to correct it?

Also i want to sum up the whole matric of both a and b and not just till index 2 of both of the 2D arrays...how to do that?

There are 2 rows and 3 columns in our array and if we run the above code which I have pasted, we don't get any error.