class LRUCache {    private int _capacity;    private int _currentSize;    private Map
     
       nodeMap;    private Node head;    private Node tail;    class Node {        public int key;        public int value;        public Node next;        public Node prev;                public Node(int k, int v) {            key = k;            value = v;        }    }    public LRUCache(int capacity) {        _capacity = capacity;        _currentSize = 0;        head = new Node(0, 0);        tail = new Node(0, 0);        tail.prev = head;        head.next = tail;        nodeMap = new HashMap<>();    }        public int get(int key) {        if (!nodeMap.containsKey(key)) {            return -1;        }        moveNode(nodeMap.get(key));        return nodeMap.get(key).value;    }        public void put(int key, int value) {        if (!nodeMap.containsKey(key)) {            if (_currentSize == _capacity) {                nodeMap.remove(tail.prev.key);                tail = tail.prev;                tail.next = null;                _currentSize--;            }            Node current = new Node(key, value);            current.next = head.next;            current.next.prev = current;            current.prev = head;            head.next = current;            nodeMap.put(key, current);            _currentSize++;        } else {            moveNode(nodeMap.get(key));            nodeMap.get(key).value = value;        }    }        private void moveNode(Node current) {        current.next.prev = current.prev;        current.prev.next= current.next;        current.next = head.next;        head.next.prev = current;        head.next = current;        current.prev = head;    }}/** * Your LRUCache object will be instantiated and called as such: * LRUCache obj = new LRUCache(capacity); * int param_1 = obj.get(key); * obj.put(key,value); */