Java Arrays.fill()

Question

How to fill a multidimensional array?

int[][] array = new int[4][6]; 
Arrays.fill(array, 0);

I tried it, but it doesn't work.

possible duplicate of [Arrays.fill with multidimensional array in Java](http://stackoverflow.com/questions/7118178/arrays-fill-with-multidimensional-array-in-java) — om-nom-nom, Aug 26 '12 at 15:17
If the array doesn't need to be a jagged array, you could create a single dimensional array (of size width * height) and just access it via `int index = (y * width) + x;` -- you could even create a class that just exposes get/set methods that take x and y as separate arguments. Then you could fill the whole array without any looping. — BrainSlugs83, Oct 06 '14 at 21:10
Possible duplicate of [Syntax for creating a two-dimensional array](http://stackoverflow.com/questions/12231453/syntax-for-creating-a-two-dimensional-array) — StarWind0, Aug 18 '16 at 17:27

aioobe · Answer 1 · 2011-03-11T17:34:45.437

31

Here's a suggestion using a for-each:

for (int[] row : array)
    Arrays.fill(row, 0);

You can verify that it works by doing

System.out.println(Arrays.deepToString(array));

A side note: Since you're creating the array, right before the fill, the fill is actually not needed (as long as you really want zeros in it). Java initializes all array-elements to their corresponding default values, and for int it is 0 :-)

edited Mar 11 '11 at 17:34

answered Mar 09 '11 at 21:59

aioobe

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for instance variables java does(automatic initalization) but not for local variables So above the above code adds importance in some cases – JAVA Sep 09 '13 at 10:50
@JoelDeWitt, why? :) – aioobe Aug 08 '16 at 02:49

score 13 · Answer 2 · answered Mar 09 '11 at 21:56

13

Try this:

for(int i = 0; i < array.length; i++) {
    Arrays.fill(array[i], 0);
}

I haven't tested it but I think it should work.

answered Mar 09 '11 at 21:56

Argote

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This is using fill for a regular int array only, hence the for loop. – Argote Feb 05 '13 at 08:54

score 2 · Answer 3 · answered Mar 09 '11 at 22:04

2

Since array is really an array of arrays, perhaps you can try looping over each row and doing fill for each one individually.

answered Mar 09 '11 at 22:04

duffymo

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score 1 · Answer 4 · edited Dec 17 '14 at 19:16

First, note that 0 is the default value for int arrays, so you don't have to fill something with 0.

If you want your array to stay truly multidimensional, you'll need a loop.

public static void fill(int[][] array, int element) {
    for(int[] subarray : array) {
        Arrays.fill(subarray, element);
    }
}

If you only need a 2D-array filled with the same element and don't want to change the subarrays later, you can use this trick:

public static int[][] create2DArray(int length, int subLength, int element) {
    int[] subArray = new int[subLength];
    Arrays.fill(subArray, element);
    int[][] array = new int[length][];
    Arrays.fill(array, subArray);
    return array;
}

This works analogously for higher-dimensional arrays.

score -3 · Answer 5 · answered Aug 18 '16 at 17:19

-3

See this way:

Arrays.fill(array[0], 0);
Arrays.fill(array, array[0]);

answered Aug 18 '16 at 17:19

GreMal

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This makes every sub-array, the exact same array, so that if you change `array[0][0]`, you also change `array[1][0]`, `array[2][0]`, ... to the same value. Not a good solution. – trincot Aug 18 '16 at 18:01

Java Arrays.fill()

5 Answers5