how to create 2D matrix of two column code example

Example 1: adding elements in a specified column or row in a two dimensional array java

package multidimensionalarrays;

public class MultidimensionalArrays {

    public static void main(String[] args) {
        double sumOfRow = 0;
        double[][] matrix = new double[3][4];
        java.util.Scanner input = new java.util.Scanner(System.in); //Scanner
        System.out.println("Enter a 3 by 4 matrix row by row: ");
        //Prompt user to enter matrix numbers
        for (int row = 0; row < matrix.length; row++) {
            for (int col = 0; col < matrix[0].length; col++) {
                matrix[row][col] = input.nextDouble();
            }
        }
        double[] sumOfCol =new double[matrix[0].length];  
        for (int i = 0; i < matrix.length; i++) { //row
            for (int j = 0; j < matrix[i].length; j++) { //column
                sumOfRow += matrix[i][j];
                sumOfCol[j] += matrix[i][j];
            }
            System.out.println("Sum of the elements at row " + row + " is: " + sumOfRow);
        }
        System.out.println("Sum of the elements at column " + col + " is: " + sumOfCol);
    }             
}

Example 2: 2d array java

//Length
int[][]arr= new int [filas][columnas];
arr.length=filas;

        int[][] a = {
            {1, 2, 3}, 
            {4, 5, 6, 9}, 
            {7}, 
        };
      
        // calculate the length of each row
        System.out.println("Length of row 1: " + a[0].length);
        System.out.println("Length of row 2: " + a[1].length);
        System.out.println("Length of row 3: " + a[2].length);
    }