java - Declare Two-Dimensional Array - Clarification -

i taking java lessons, , course explaining two-dimensional arrays. first method declaring type of variable create constant arguments how many rows , columns in two-dimensional array. then, used nested for-loop give random numbers particular rows, , columns.

the second method declare , initialize two-dimensional array "int[][] nums" line below. know has 3 rows. it's similar putting list in bigger list, how many columns in "nums" array? there may simple answer, little confused right now. thank assistance.

import java.util.random; //importing class package  public class chap15part4 {     public static void main(string[] args)     {         final int rows = 5; //constant         final int cols = 5; //constant         int[][] numbers = new int[rows][cols]; //declaring 2-d array       constants arguments         random rand = new random(system.currenttimemillis()); //seeding random number generator         for(int r = 0; r < rows; ++r) //nested for-loop assign numbers elements             (int c = 0; c < cols; ++c)                 numbers[r][c] = rand.nextint(101);           int[][] nums = {{10,20,30,40}, {20,30,40,50}, {30,40,50,60}}; //declaring & initializing 2-d array     }  } 

there 4 columns. matrix this, can count columns easily:

{{10, 20, 30, 40},  {20, 30, 40, 50},  {30, 40, 50, 60}}