how to sum values in columns in a 2D array?

[ccarter45]

public class SumColumn 
{
  public static void main( String[] args ) 
  {
    int[][] grid = {{1, 2, 3}, {4, 5, 6}}; // array initializer for 2D array
    
    print2DArray("The array is: ", grid);
    
    sumColumn(grid);// write method call to sumColumn here
  }
   
  // print out a 2D array
  public static void print2DArray( String message, int[][] a )
  {
    System.out.println(message);
    
    for ( int i = 0; i < a.length; i++ )
    {
      for ( int j = 0; j < a[0].length; j++ )
      {
        System.out.print(a[i][j] + " ");
      }
      System.out.println();
    }
  }
  
  // sums up 2D array elements column by column
  public static void sumColumn( int[][] a )
  {
int rows = 2;
int columns = 3;
    
    
    // nested for loop sums up each row
    int total;
    for( int i = 0; i < a.length; i++ )             // go down rows
    {
      total = 0;
      for( int j = 0; j < a[i].length; j++ )        // print every element in a row
      {          
        total = total + a[i][j];
      }
      System.out.printf( "Column %d sums up to %d.\n", i, total);  
    }
  }
}