[leetcode] LRU Cache

import java.util.HashMap;

public class LRUCache {
    private int capacity;
    private int len;
    private HashMap<Integer, DoubleLinkedListNode> map = new HashMap<Integer, DoubleLinkedListNode>();
    private DoubleLinkedListNode head;
    private DoubleLinkedListNode tail;

    public LRUCache(int capacity) {
        this.capacity = capacity;
        len = 0;
    }

    public int get(int key) {
        if (map.containsKey(key)) {
            DoubleLinkedListNode cur = map.get(key);
            removeNode(cur);
            setHead(cur);
            return cur.val;
        } else
            return -1;
    }

    public void set(int key, int value) {
        if (map.containsKey(key)) {
            DoubleLinkedListNode cur = map.get(key);
            cur.val = value;
            removeNode(cur);
            setHead(cur);
        } else {
            DoubleLinkedListNode newNode = new DoubleLinkedListNode(key, value);
            if (len < capacity) {
                setHead(newNode);
                map.put(key, newNode);
                len++;
            } else {
                map.remove(tail.key);
                tail = tail.pre;
                if (tail != null)
                    tail.next = null;

                setHead(newNode);
                map.put(key, newNode);

            }

        }
    }

    private void removeNode(DoubleLinkedListNode cur) {
        if (cur == null)
            return;
        DoubleLinkedListNode pre = cur.pre;
        DoubleLinkedListNode next = cur.next;
        if (pre != null) {
            pre.next = cur.next;
        } else
            head = next;

        if (next != null)
            next.pre = cur.pre;
        else
            tail = pre;

    }

    private void setHead(DoubleLinkedListNode cur) {
        cur.next = head;
        cur.pre = null;
        if (head != null)
            head.pre = cur;

        head = cur;
        if (tail == null)
            tail = cur;
    }

    public static void main(String[] args) {
        LRUCache cache = new LRUCache(1);
        cache.set(1, 11);
        cache.set(1, 111);
        System.out.println(cache.get(1));
        cache.set(2, 22);
        System.out.println(cache.get(1));
        System.out.println(cache.get(2));
    }

    private static class DoubleLinkedListNode {
        public int key;
        public int val;
        public DoubleLinkedListNode pre;
        public DoubleLinkedListNode next;

        public DoubleLinkedListNode(int key, int val) {
            this.key = key;
            this.val = val;
        }
    }

}