how to create a 2d array in java

1char[][] array = new int[rows][columns];

1int[][] arr = new int[row][column]; 

1//Length
2int[][]arr= new int [filas][columnas];
3arr.length=filas;
4
5        int[][] a = {
6            {1, 2, 3}, 
7            {4, 5, 6, 9}, 
8            {7}, 
9        };
10      
11        // calculate the length of each row
12        System.out.println("Length of row 1: " + a[0].length);
13        System.out.println("Length of row 2: " + a[1].length);
14        System.out.println("Length of row 3: " + a[2].length);
15    }

1 int[][] arr = new int[m][n]; 

1 int[][] arr = new int[10][20]; 
2        arr[0][0] = 1;