Initialization of 2D Array in Java?

Question

I've a little confusion, when we declare & initialize a 2D array in java like given below

int arr[][]={{1,2,3,4},{4,3,2,1}};

This work correct, but when do do the above action like given below

int arr[2][4]={{1,2,3,4},{4,3,2,1}};

Then why it generates an error? Why can't we fix the size of rows and columns and then assign values in same statement? I know that we can do that separately using loops, something like arr[0][0]=345; and so on, but why can't we do it like this?

int arr[4][2]={{1,2,3,4},{4,3,2,1}};

You can't do it, because that is simply not how Java is designed. Asking why that is, is asking for opinions, which is off-topic. As an aside, although putting array brackets on the variable name is possible in Java, the recommended way is to put them on the type, so int[][] arr instead of int arr[][]. — Mark Rotteveel
– Mark Rotteveel, Commented Aug 1, 2021 at 10:33

Auktis · Accepted Answer · 2021-08-01 10:30:13Z

4

That’s because Java is not C language.
When you write int arr[][] = {{1, 2, 3, 4}, {4, 3, 2, 1}};, you declare and initialize a multidimensional array of 2 by 4. It is equivalent to the C language initialization you proposed (int arr[2][4] = {{1, 2, 3, 4}, {4, 3, 2, 1}};)

In Java, we preferably declare arrays in a Java-style manner:

int[][] arr = {{1, 2, 3, 4}, {4, 3, 2, 1}};

where int[][] is just a type identifier, we cannot specify size.
Moreover, in Java, we can initialize a 2D array that is not rectangular:

int[][] arr = {{1, 2, 3, 4}, {4, 3}};

If you want to declare an array of specific size, but don’t want to specify all it’s values at once, the only solution is to use new:

int[][] arr = new int[2][4];
arr[0][0] = 1;

edited Aug 1, 2021 at 10:30

answered Aug 1, 2021 at 10:09

Auktis

5552 silver badges14 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Initialization of 2D Array in Java?

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related