Can the rows in a two-dimensional array have different lengths?

Show the output of the following code: int[][][] array = {{{1, 2}, {3, 4}}, {{5, 6},{7, 8}}}; System.out.println(array[0][0][0]); System.out.println(array[1][1][1]);

Write a method that sums all the numbers in the major diagonal in an $n * n$ matrix of double values using the following header:

public static double sumMajorDiagonal(double[][] m)

Write a test program that reads a 4-by-4 matrix and displays the sum of all its elements on the major diagonal. Here is a sample run:

Enter a 4-by-4 matrix row by row:
1 2 3 4.0   <enter>
5 6.5 7 8   <enter>
9 10 11 12  <enter>
13 14 15 16 <enter>
Sum of the elements in the major diagonal is 34.5

Write the following method that tests whether a two-dimensional array has four consecutive numbers of the same value, either horizontally, vertically, or diagonally:

Public static boolean isConsecutiveFour(int[][] values)

(Shuffle rows) Write a method that shuffles the rows in a two-dimensional int array using the following header:

public static void shuffle(int[][] m)

Write a test program that shuffles the following matrix:

int[][] m = {{1, 2}, {3, 4}, {5, 6}, {7, 8}, {9, 10}};