Java - Adding element at specific index and pushing other elements down

Question

This feature is supposed to add an element at the selected index and push all other in the array elements down. So, for instance, say I have the following array:

[0] = zero
[1] = one
[2] = two

if I add another element at index 0 called NEWZERO, the array has to look like this:

[0] = NEWZERO
[1] = zero 
[2] = one 
[3] = two

but currently I'm getting IndexOutOfBounds exception and it doesn't work.

P.S. I don't want to use the built-in ArrayList library, which automatically does it for you.

    public void insert(int i, String s) {

    if (array[i] == null) {
        array[i] = s; //Need to add feature that instantly puts the element at the first available spot on the list.
    } else { 
        for (int j = i; j < array.length; j++) { //Can't use >= i
            array[j + 1] = array[j];

            if (j == array.length - 1) { 
                break;
            } 
        }
        array[i] = s;

YOu need to enlarge your array to avoid exception: Check – Areo Nov 13 '13 at 14:27 — Areo, Nov 13 '13 at 14:27

Dimitar Pavlov · Accepted Answer · 2013-11-13T14:58:51.407

3

Try this

public void insert(int i, String s) {

    String[] newArr = new String[array.length + 1];
    for (int j = 0; j < array.length; j++) { 
        if(j < i){
           newArr[j] = array[j];
        } else if(j == i){ // '==' insted of '='
           newArr[j] = s;
        } else {
           newArr[j+1] = array[i];
        }
    }

    array = newArr;
}

edited Nov 13 '13 at 14:58

answered Nov 13 '13 at 14:35

Dimitar Pavlov

300
3
10

this will be a big performance loss as on each insert a new array is being allocated. A better option would be to use ArrayList and not reinvent the wheel. – Narendra Pathai Nov 13 '13 at 14:37
Yes I know but "P.S. I don't want to use the built-in ArrayList library, which automatically does it for you. " – Dimitar Pavlov Nov 13 '13 at 14:41

score 1 · Answer 2 · answered Nov 13 '13 at 14:29

1

Well, arrays are not dynamic, so if you have an array that has size 3 you cannot add anything to it unless you create a new array that has size of oldArray.length+1 and then populate it with new data.

answered Nov 13 '13 at 14:29

Lucas

3,181
4
26
45

Karthik Joshi S · Answer 3 · 2019-02-16T19:25:36.773

0

public static int[] addAtIndex(int[] a, int index, int value) {
 int[] newArr = new int[a.length + 1];
 int temp;
 for (int j = 0; j < a.length + 1; j++) {
  if (j < index) {
   newArr[j] = a[j];
  } else if (j == index) {
   //copy value at index to temp so that value added at specific index can be shifted right
   temp = a[j];
   newArr[j] = value;
   newArr[j + 1] = temp;
  } else {
   newArr[j] = a[index];
   index++;
  }
 }
 return newArr;
}

edited Feb 16 '19 at 19:25

answered Feb 16 '19 at 16:05

Karthik Joshi S

11
1
5

Adds element at specific index and right shifts other elements. – Karthik Joshi S Feb 16 '19 at 16:07
Nice job answering! You could really bump the quality of your answer if you added a small comment explaining your code in the answer. – Patrick Hollweck Feb 16 '19 at 16:17

Java - Adding element at specific index and pushing other elements down

3 Answers3