Question

Can anyone help me with Arrays in JAVA?

Answer 1

@LolGoCryAboutIt

Answer 2

What did you need help with exactly?

Answer 3

I.E. Do you have a sample problem, so something specifically that you're confused about?

Answer 4

I want to know how to create 2-D arrays

Answer 5

Okay, let's start with that.

Answer 6

Do you conceptually understand what a 2D array is?

Answer 7

Yes a array consisting of rows and columns

Answer 8

Exactly. Now, do you know how to create a one-dimensional array in Java?

Answer 9

Yes

Answer 10

Okay, show me how you would create a 1D array consisting of 5 rows.

Answer 11

For 5 rows, I can use like: type var[]; var = new type[5]; or for an auto array, I can use type var[] = {.....};

Answer 12

Perfect!

Okay, now for a multidimensional array, all that means is, each index in your var array will also be an array.

So for example, let me declare a 2D array like so:

int[ ][ ] var = new int[5][3];

Answer 13

Okay..

Answer 14

Now, within var you have row indexes 0-4.

You can think of a multidimensional array like so:

var[0] consists of items var[0][0], var[0][1], var[0][2]
var[1] consists of items var[1][0], var[1][1], var[1][2]
var[2] consists of items var[2][0], var[2][1], var[2][2]
var[3] consists of items var[3][0], var[3][1], var[3][2]
var[4] consists of items var[4][0], var[4][1], var[4][2]

Answer 15

So in essence, each row (ex. var[2]) is an array of items, which we call a column.

Answer 16

Do you know how to set up a loop for a 1D array to initialize values?

Answer 17

No

Answer 18

Could you explain?

Answer 19

I can - but first let me ask - do you know how to work with loops (while loops, for loops, etc.)?

Have you been using loops to set up your array, or, are you setting your values like so:
var[0] = 5;
var[1] = 12;

?

Answer 20

Yeah I know how to set loops. But I don't know how to set loops for arrays. I have been using the 1-D arrays like the one you have said above

Answer 21

If you want to set your values, you just do the following, just like a 1D array:

(FYI I'm just picking random integers to set the array indexes to)

var[0][0] = 12;
var[0][1] = 4;
var[0][2] = 17;

var[1][0] = 81;
var[1][1] = 0;
var[1][2] = 46;

var[2][0] = 65;
var[2][1] = 82;
var[2][2] = 19;

var[3][0] = 90;
var[3][1] = 11;
var[3][2] = 7;

var[4][0] = 30;
var[4][1] = 44;
var[4][2] = 64;

Answer 22

This is similar to:

var[0] = 7;
var[1] = 80;
var[2] = 5;
var[3] = 100;
...etc.

Except that now, for every "row" you have a certain number of columns to set.

i.e.

var[0] has 3 columns. Hence, we need to set var[0][0], var[0][1], and var[0][2]

Answer 23

Let me know if you are confused or need any further explanation

Answer 24

Yeah. I have declared the numbers as you said

Answer 25

That's it! Your 2D array is all set to be used.

Just use the 2D array like so:

someNumber = int[1][2];
//someNumber now equals 46

Answer 26

And I have added this System.out.println(var[0][1]); at the last to print out 4

Answer 27

Yup! That should work!

Answer 28

Yes. It did work. Is there a Auto-array for 2-D also?

Answer 29

There is - but I have never done so. Let me look at how it's done.

Answer 30

Okay. Sure

Answer 31

Okay, so I wrote a quick program to confirm, and you can set it up like this:

int var[][] = {{1,2,3},{4,5,6}};

Answer 32

That's the equivilent to:

var[0][0] = 1;
var[0][1] = 2;
var[0][2] = 3;

var[1][0] = 4;
var[1][1] = 5;
var[1][2] = 6;

Answer 33

Oh okay. Thanks a ton. Are you available tomorrow?

Answer 34

I'm on randomly. Just tag my name, if I'm on I'll respond!

Answer 35

Okay. I live in India its about 11:36 PM. Time to sleep. I'll text you tomorrow. Bye. And thanks again for the help

Answer 36

No problem, have a good night!

Answer 37

Thank you :)