2d array java

Two dimensional array:
int[][] twoD_arr = new int[10][20];

Three dimensional array:
int[][][] threeD_arr = new int[10][20][30];
 int[][] arr = new int[m][n]; char[][] array = new int[rows][columns];int[][] arr = new int[row][column]; //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);
    }