Use Arrays when initializing another Array at specific position

user_13717785 0
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I have an integer array. int[] arr1 = new int[] {3, 4, 5};. I want to insert this array when initializing another array. So that when int[] arr2 = new int[] {8, 7, arr1, 1, 0};, arr2 will equal {8, 7, 3, 4, 5, 1, 0}.

Also, I do not know the length of arr1, so I can't do int[] arr2 = new int[] {8, 7, arr1[0], arr1[1], arr1[2], 1, 0};

Any help is greatly appreciated.

integer arrays java
3 Answers

Sadly as far as I'm aware something like that can't be done in a single operation. The best I was able to come up with is to create a result array. Then you copy to it first part of arr2, whole arr1 and finally second part of arr2. In the end whole method would look like so:

private static int[] insertArrayAtPosition(int[] arr1, int[] arr2, int insertPos){
    int[] result = new int[arr1.length + arr2.length];
    System.arraycopy(arr2, 0, result, 0, insertPos);
    System.arraycopy(arr1, 0, result, insertPos, arr1.length);
    System.arraycopy(arr2, insertPos, result, insertPos + arr1.length, arr2.length - insertPos);
    return result;
}

And then you can call it like so:

public static void main(String args[]) {
    int[] arr1 = new int[] {3, 4, 5};
    int[] arr2 = new int[] {8, 7, 1, 0};
    int[] result = insertArrayAtPosition(arr1, arr2, 2);
    System.out.println(Arrays.toString(result));
}

Edit: Milgo's solution looks much better. However, mine allows to insert one array into another at specific position after they are already created. Which one to use depeds on the usecase.

user_49497500

You could use ArrayUtils.addAll() three times.

int[] arr1 = new int[] {3, 4, 5};
int[] arr2 = new int[arr1.length + 4];
ArrayUtils.addAll(arr2, new int[]{8, 7});
ArrayUtils.addAll(arr2, arr1);
ArrayUtils.addAll(arr2, new int[]{1, 0});

ArrayUtils is part of Apache Commons.

user_32754410

This is not natively supported in java / there is no language feature that allows you to use a one liner. You can of course write a loop that inserts the elements of the other array, you can also use list interfaces or Arrays#stream. The best way to do it should probably be to use lists, like this:

List<Integer> arr1 = Arrays.asList(3, 4, 5);
List<Integer> arr2 = Arrays.asList(8, 7, 1, 0);
arr2.addAll(2, arr1);

Hope this helpes.

Edit: It is a one liner btw :)

user_130653800
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