ArrayList — resizable array with O(1) random access. LinkedList — doubly linked list with O(1) insertion/removal at ends.Vivid analogy: ArrayList is a filing cabinet — opening drawer #5 is instant. LinkedList is a chain of folders — finding #5 means opening the first four.Why it matters: ArrayList is the default collection for good reason — contiguous memory makes it faster for nearly all operations due to CPU cache prefetching.javaArrayList<Integer> al = new ArrayList<>();al.add(1); // O(1) amortizedal.get(0); // O(1) — direct index lookupal.add(0, 10); // O(n) — must shift elementsLinkedList<Integer> ll = new LinkedList<>();ll.add(1); // O(1) — append to tailll.get(0); // O(n) — must traverse from headll.addFirst(10); // O(1) — prepend to head- ArrayList — preferred for most scenarios (read-heavy, indexed access).- LinkedList — useful as Queue/Deque implementation.