Assign elements into Random index in ArrayList

Do NOt close this question again. This is different from generating random numbers

I want to put elements in an ArrayList(), but I have to put each elements in random index. I cannot use any shuffle methods and others, such as maps, hashset, etc.

However, When I try to add element in random index, I get indexOutOfBoundsException error.

 private void addRandomlyArray(ArrayList<Integer> t, int size){
     Random rand = new Random();
     for(int i = 0; i<size; i++)
         int rad = rand.nextInt(size);
         t.add(rad,rad);
     }
}

Also, For the linkedList, I get same error.

  private void addRandomlyLinked(LinkedList<Integer> t,int leng){
      Random rand = new Random();
      for (int i = 0; i<leng; i++){
          int rad = rand.nextInt(leng);

          t.add(rad,rad);
     }

} When I put elements into index in array, How can I put these elements into randomly assigned index?