ArrayList — backed by a resizable array. LinkedList — backed by a doubly linked list of nodes.Vivid analogy: ArrayList is a row of mailboxes numbered 1 to N — open mailbox #50 instantly. LinkedList is a scavenger hunt — each clue leads to the next, so finding #50 means following 49 clues.Why it matters: ArrayList provides O(1) random access. LinkedList provides O(1) insertion at known positions, but node traversal overhead makes it slower in practice.javaArrayList<Integer> al = new ArrayList<>();al.add(1); al.add(2); al.add(3);al.get(0); // O(1) — instant by indexLinkedList<Integer> ll = new LinkedList<>();ll.add(1); ll.add(2); ll.add(3);ll.get(0); // O(n) — must traverse from headll.addFirst(0); // O(1)ll.removeFirst(); // O(1)- ArrayList — preferred for most scenarios.- LinkedList — only for frequent add/remove at both ends.