When should you use ArrayList and when LinkedList?

The choice between ArrayList and LinkedList depends on the nature of operations and performance requirements:

• ArrayList:

  • Based on an array.
  • Fast access by index (O(1)).
  • Slow insertions and deletions in the middle of the list (O(n)), as elements need to be shifted.
  • Better suited if quick random access is often needed and size rarely changes.

• LinkedList:

  • Implemented as a doubly linked list.
  • Slow access by index (O(n)), as traversal is required.
  • Fast insertions and deletions at the beginning or middle of the list (O(1)), if a reference to the node is available.
  • Suitable if you frequently add/remove elements in the middle or beginning, and quick random access is not necessary.