What collections do you know? List the implementations of collections.

In Java, collections are data structures for storing and managing groups of objects. The main collection interfaces and their implementations:

• List — an ordered list with the possibility of duplicate elements.

  • ArrayList — a dynamic array, quick access by index.
  • LinkedList — a doubly linked list, efficient addition/removal in the middle.

• Set — a collection of unique elements, without order (or with a specific order).

  • HashSet — based on a hash table, fast search.
  • LinkedHashSet — preserves insertion order.
  • TreeSet — a sorted set based on a red-black tree.

• Queue — a queue for processing elements in FIFO order.

  • LinkedList — implements Queue.
  • PriorityQueue — a priority queue.

• Deque — a double-ended queue.

  • ArrayDeque — an efficient implementation of Deque.

• Map — a key-value mapping (not a subclass of Collection).

  • HashMap — a hash table.
  • LinkedHashMap — preserves insertion order.
  • TreeMap — a sorted map.

Each implementation is optimized for different usage scenarios, for example, ArrayList is better for frequent index access, while LinkedList is better for frequent insertions/deletions.