What is difference between ArrayList and LinkedList ?

The difference between ArrayList and LinkedList in Java revolves around their internal data structures, performance implications, and suitable use cases. Both ArrayList and LinkedList implement the List interface, but they do so in fundamentally different ways, which affects their performance for various operations such as adding, removing, and accessing elements.

Internal Data Structures

• ArrayList: It uses a dynamic array to store its elements. This means that elements in an ArrayList are stored in contiguous memory locations, which allows for fast random access of elements using an index. The ArrayList dynamically resizes itself by creating a new larger array and copying the old elements to the new array if the initial capacity is exceeded[1][2][3][4][5].

• LinkedList: Unlike ArrayList, LinkedList uses a doubly linked list to store its elements. Each element (node) in a LinkedList contains three parts: the data, a reference to the next node, and a reference to the previous node. This structure allows for efficient insertion and removal of elements at the cost of slower random access[1][2][3][4][5].

Performance Implications

• Access Time: ArrayList provides $$O(1)$$ time complexity for accessing an element as it allows direct access based on the index. On the other hand, LinkedList has $$O(n)$$ time complexity for accessing elements, as it needs to traverse the list from the beginning or the end (whichever is closer) to access the desired element[1][2][3][4][5].

• Insertion/Deletion: Insertion or deletion of elements in an ArrayList can be slow, especially if the operation is performed at the beginning or in the middle of the list, as it requires shifting the rest of the elements. In c...