Java native arrays length

Question

I have a two-dimensional array of doubles in Java, which is basically a table of values, and I want to find out how many rows it has ...

It is declared elsewhere (and allocated) as follows:

double[][] table;

then passed to the function ...

private void doSomething(double[][] table)
{

}

In my function, I want to know the length of each dimension without having to pass them as arguments. I can do this for the number of columns, but don't know how to do this for rows ...

int cols = table[0].length;
int rows = ?;

How to do it?

Can I just say ...

int rows = table.length;

Why won't this give an x ​​cols string?

Answer 1

In Java, a 2D array is nothing more than an array of arrays.

This means that you can easily get the number of lines like this:

int rows = array.length;

, (.. ).

int columnsInFirstRow = array[0].length;

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Jagged Array.

Answer 2

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Answer 3

. , Java .

table.length , ( , ).

table[0].length . , NullPointerException ( , new double[rows][cols]).

Answer 4

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int rows = table.length;

?

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double[][] foo = { double[] = {...}, double[] = {...}, ... }

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Answer 5

, . table.length

Answer 6

Alternatively, you can combine your 2d array into a Matrix or Grid class. Internally, you can represent it as a 1d array and calculate the offsets for the row / column coordinates.