How to make a 2D array of 2D arrays

Question

I tried to find a solution for this through many sources. But in vain. I have 3 2D array objects:

double[][] W1 = new double[5][10];
double[][] W2 = new double[2][3];
double[][] W3 = new double[4][6];

and I want another array object to contain those 3 array objects. How do I do it?

I found that it is possible to make many 1D arrays to an array of 2D arrays using the following

double[][] W = new double[][]{W1, W2, W3}; //provided W1, W2, W3 are 1D arrays.

But how do I do the same for 2D arrays?

Answer 1

A 1D array is declared as double[], i.e. [] of double.

A 1D array of 1D arrays (a 2D array) is declared as double[][], i.e. [] of double[].

A 1D array of 2D arrays (a 3D array) is declared as double[][][], i.e. [] of double[][].

A 1D array of 3D arrays (a 4D array) is declared as double[][][][], i.e. [] of double[][][].

There is no practical distinction between a 3D array, a 1D array of 2D arrays and a 2D array of 1D arrays; or between a 4D array, a 1D array of 3D arrays and a 2D array of 2D arrays. It's purely how you choose to think about them.

I really can't think why you'd want to use arrays nested this deeply; I'd suggest you think about whether a better alternative might be exist.

Answer 2

So you want to initialize a 3D array from 3 2D arrays. That should do it

double[][][] W = {W1, W2, W3};

Note how you don't need new.