Insert at a specific index in array

Question

So I want to insert a value in a specific index, that mean I would throw exception if the index I want to insert is not exist or bigger than size, otherwise, I would use this method to ensure the capacity of the array is not null:

private void ensureCapacity(int size_wanted)
{
  int max_capacity = storage.length;
  if (size_wanted > max_capacity) 
  {
    max_capacity = max_capacity * GROW_FACTOR +1; 
    storage = Arrays.copyOf(storage, max_capacity); // increases array size + copy contents
  } 
}

Then at this point, I suppose to extend the array and already made a copy of my original with the increased size already, right?

All I need to do is using a loop and shift everything to the right by one, to leave space for the index I want to insert at, correct?

ArrayList contains dynamic array implementation you are doing is already there. — Amit Deshpande
– Amit Deshpande, Commented Oct 3, 2012 at 4:28
"not exist or bigger than size". You mean >= size actually, remembering that indexes are 0-based. — user207421
– user207421, Commented Oct 3, 2012 at 10:26

Amit Deshpande · Accepted Answer · 2012-10-03 04:28:13Z

1

You can use System.arrayCopy to move array like that. but why are you rebuilding existing functionality provided by ArrayList

answered Oct 3, 2012 at 4:28

Amit Deshpande

19.2k4 gold badges48 silver badges72 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Ted Hopp · Accepted Answer · 2012-10-03 04:28:24Z

1

You don't need to use a loop; you can use the method System.arraycopy to move elements within an array. It correctly handles overlapping ranges:

System.arraycopy(storage, insertPos, storage, insertPos+1, oldSize - insertPos);

answered Oct 3, 2012 at 4:28

Ted Hopp

235k48 gold badges412 silver badges533 bronze badges

2 Comments

Ryoko Nela Over a year ago

But then again I cant put the last 2 argument inside, since I cant change an already prep method.

Ted Hopp Over a year ago

@RyokoNela - After calling ensureCapacity, call System.arraycopy (using whatever variable names you are using). Then you assign the new value to the slot that was just created: storage[insertPos] = insertValue;.

Collectives™ on Stack Overflow

Insert at a specific index in array

2 Answers 2

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related