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javaarrays
Liftoff
Liftoff

Reputation: 25412

Java using array[] to assign to next index

So I know that Java treats arrays' sizes as immutable, but in other languages like PHP, I have been able to use [] to assign a value to the next index of an array:

PHP:

$arr = array();

//Arr looks like this
$arr => {}

$arr[] = "Value";

//Arr looks like this
$arr => {"Value"}

Is there a similar function in Java?

int[] arr = new int[0];
arr[] = 3;
arr[] = 4;

//arr => [3, 4];

Upvotes: 0

Views: 3631

Answers (5)

Dave Delay
Dave Delay

Reputation: 1320

In Java you have to set the number of elements in the array when you construct it. So you can't append more elements to the end of an array.

You can do the following to move to the next element in the array:

int[] arr = new int[2];
int = 0;
arr[i++] = 3;
arr[i++] = 4;

That works because i is incremented after each array element is assigned.

If you really want to append to the end of a list, you should use a Java collection class. Unfortunately you can't have a collection of primitive types (like int).

Upvotes: 0

mdewitt
mdewitt

Reputation: 2534

In java you have to set the size of the Array when you create it

int[] arr = new int[2];

Then once the array is created, you can add values to a specific index like this:

arr[0] = 3;
arr[1] = 4;
//Now arr = {3, 4}

However, you cannot add a third value to the array arr because the size is fixed at 2. If you need to change the size of the array, an ArrayList would be better. You can just use the add() method and it will add values to the end of the array

ArrayList<Integer> arr = new ArrayList<Integer>();
arr.add(3);
arr.add(4);
arr.add(5);
//Now arr contains the values {3, 4, 5}
//You can continue you add values

EDIT: Another option is to use the Arrays.copyOf(int[] arr, int size)

int[] arr = {3, 4};
//arr contains the values {3, 4}
int[] arr2 = Arrays.copyOf(arr, 4);
//arr2 contains the values {3, 4, 0, 0}

Upvotes: 6

aquemini
aquemini

Reputation: 960

As has been said, Java arrays cannot be resized. However, if you used ArrayList<Integer>, you could use the add() function to get the desired result.

Upvotes: 2

Bohemian
Bohemian

Reputation: 425298

Almost. There is a shorthand syntax for array creation:

int[] arr = {3, 4};

Otherwise use a List which resizes automatically:

List<Integer> list = new ArrayList<>();
list.add(3);
list.add(4);
// etc

Upvotes: 0

Dima
Dima

Reputation: 8662

no. you have to use your own index or use an ArrayList and the add method

Upvotes: 0

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