What is the Difference Between ArrayList and LinkedList?

ArrayList and LinkedList are two popular data structures in Java that are used to store and manage collections of objects. They have different strengths and weaknesses, and the choice between them depends on the specific needs of your application.

Here are the key differences between ArrayList and LinkedList:

1. Internal Implementation: ArrayList uses a dynamic array to store its elements, while LinkedList uses a doubly linked list to store its elements.
2. Manipulation: ArrayList is slower in manipulation due to the array manipulation, while LinkedList is faster in manipulation because it is node-based and does not require much bit shifting.
3. Access: ArrayList is faster in storing and accessing data because it is derived from an array, while LinkedList is slower in accessing specific elements due to its scattered data.
4. Memory Efficiency: ArrayList is more memory-efficient as it does not require extra space for the additional link structure present in LinkedList.
5. Cache-friendliness: ArrayList has better cache-locality and is more cache-friendly than LinkedList due to its compact data storage.
6. Implementation: ArrayList implements only the List interface, while LinkedList implements both the List and Queue interfaces, allowing it to act as a queue as well.

In summary, use ArrayList when you need fast random access and don't need to do a lot of insertion and deletion. Use LinkedList when you need fast insertion and deletion and don't need to do a lot of random access.

Comparative Table: ArrayList vs LinkedList

Here is a table comparing the differences between ArrayList and LinkedList:

ArrayList internally uses a dynamic array to store elements, and its memory location for the elements is contiguous. LinkedList, on the other hand, uses a doubly linked list structure, and the location for the elements is not contiguous. ArrayList provides efficient index-based access, while LinkedList uses pointer-based access.

Insertion and deletion operations are more efficient at the end of an ArrayList, but they are expensive in the middle. In contrast, LinkedList offers efficient insertion and deletion operations throughout the list. Retrieval operations are efficient in ArrayList, but they are costly in LinkedList, especially for random access.

ArrayList has better cache locality and is more cache-friendly, while LinkedList has worse cache locality and is less cache-friendly. Both ArrayList and LinkedList are non-synchronized, meaning they are not thread-safe and should not be used concurrently without proper synchronization.