How to add an element to Array and shift indexes?

Question

I need to add an element to Array specifying position and value. For example, I have Array

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

after applying addPos(int 4, int 87) it should be

int []a = {1, 2, 3, 4, 87, 5};

I understand that here should be a shift of Array's indexes, but don't see how to implement it in code.

Answer 1

This should do the trick:

public static int[] addPos(int[] a, int pos, int num) {
    int[] result = new int[a.length];
    for(int i = 0; i < pos; i++)
        result[i] = a[i];
    result[pos] = num;
    for(int i = pos + 1; i < a.length; i++)
        result[i] = a[i - 1];
    return result;
}

Where a is the original array, pos is the position of insertion, and num is the number to be inserted.

Answer 2

The most simple way of doing this is to use an ArrayList<Integer> and use the add(int, T) method.

List<Integer> list = new ArrayList<Integer>();
list.add(1);
list.add(2);
list.add(3);
list.add(4);
list.add(5);
list.add(6);

// Now, we will insert the number
list.add(4, 87);