```val s: Array<LongArray> = Array(5) { LongArray(10) } println("size" + s[0].size)``` is this...

# getting-started

[althaf]

val s: Array<LongArray> = Array(5) { LongArray(10) }
println("size" + s[0].size)

is this the only way to get col size ^^

[Klitos Kyriacou]

This is an array of arrays. Each row can have a different-sized column. s[0].size is the number of columns in the first row. Also, note that your initializer, Array(5) { LongArray(10) } initializes an array of 5 rows, with the first row being a LongArray of 10 columns, and the remaining rows being null.

[althaf]

@Klitos Kyriacou so to declare some thing like java

Long [] [] matrix , how can we do this in kotlin

[althaf]

Array(5) { LongArray(10) }
[0] [0] ........ [9]
[1] nul
[3] nul
[4] nul
Did you meant to say this declaration end like this in memory ?
and not
[0] [0] ........ [9]
[1] [0] ........ [9]
[3] [0] ........ [9]
[4] [0] ........ [9]

[Klitos Kyriacou]

Sorry, you're right, it's the latter. Ignore my original reply as it's wrong.

[Stephan Schroeder]

Klitos' post isn't completely wrong though. not every column needs to be the same length. You could define a triangular matrix like this:

Array(5) { LongArray(it+1) }

generates
[0] [0]
[1] [0][1]
[2] [0] ...[2]
...
[4] [0] ........ [4]

[nkiesel]

yes: an Array<Array> is not the same as a matrix because every row can have a different size. You can count the number of "cells" using `s.sumOf { it.size }`which also works (though slightly less efficient than s.size * s[0].size) for an array where all rows have the same length.

[althaf]

Thank you @Klitos Kyriacou @Stephan Schroeder @nkiesel for your valuable time at replying my question 🙂