How Is The Performance Of An Arraylist?

1.	How Is The Performance Of An Arraylist?
Answer» Adding an element - If you are adding at the end using ADD(E e) method it is O(1). In the worst case it may go to O(n). That will happen if you add more elements than the capacity of the underlying array. Retrieving an element - Since ArrayList INTERNALLY uses an array to store elements so get(int index) means going to that index directly in the array. So, for ArrayList get(int index) is O(1). Removing an element - If you are removing using the remove(int index) method then, in case of ArrayList getting to that index is fast but removing will MEAN shuffling the remaining elements to fill the gap CREATED by the removed element with in the underlying array. Thus it can be said remove(int index) OPERATION is O(n - index) for the arraylist.

Answer»

Adding an element - If you are adding at the end using ADD(E e) method it is O(1). In the worst case it may go to O(n). That will happen if you add more elements than the capacity of the underlying array.
Retrieving an element - Since ArrayList INTERNALLY uses an array to store elements so get(int index) means going to that index directly in the array. So, for ArrayList get(int index) is O(1).
Removing an element - If you are removing using the remove(int index) method then, in case of ArrayList getting to that index is fast but removing will MEAN shuffling the remaining elements to fill the gap CREATED by the removed element with in the underlying array. Thus it can be said remove(int index) OPERATION is O(n - index) for the arraylist.

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