solved 'LRU cache' on LeetCode http://oj.leetcode.com/problems/lru-cache/

LRUCache.java

import java.util.HashMap;
import java.util.Map;

/**
 * Created with IntelliJ IDEA.
 * User: EDFward
 * Date: 11/17/13
 * Time: 12:52 AM
 * Happy coding!
 */
class DLinkedItem {
    public DLinkedItem(int val, int k) {
        this.val = val;
        this.k = k;
    }
    public int getK() { return k; }

    public DLinkedItem prev;
    public DLinkedItem next;
    public int val;
    private int k;
}

class DLinkedList {
    public DLinkedItem front, end;

    public DLinkedList() {
        front = new DLinkedItem(-9999, -9999);
        end = new DLinkedItem(-9999, -9999);
        end.next = front;
        front.prev = end;
    }

    public void moveToFront(DLinkedItem d) {
        d.prev.next = d.next;
        d.next.prev = d.prev;
        front.prev.next = d;
        d.prev = front.prev;
        front.prev = d;
        d.next = front;
    }

    public void addToFront(DLinkedItem d) {
        front.prev.next = d;
        d.prev = front.prev;
        front.prev = d;
        d.next = front;
    }

    public int removeLeast() {
        DLinkedItem least = end.next;
        int res = least.getK();
        end.next = least.next;
//        least.next.prev = front; // f**k my bug!
        least.next.prev = end;
        return res;
    }

    public void printList(Boolean reverse) { // for debug
        if (!reverse) {
            DLinkedItem d = end.next;
            while (d != front) {
                System.out.print(d.getK()+" ");
                d = d.next;
            }
        }
        else {
            DLinkedItem d = front.prev;
            while (d != end) {
                System.out.print(d.getK()+" ");
                d = d.prev;
            }
        }
    }
}


public class LRUCache {
    public static void main(String[] args) {
        LRUCache lru = new LRUCache(3);
        lru.set(1,1);lru.set(2,2);lru.set(3,3);lru.set(4,4); lru.get(4);lru.get(3);lru.get(2);lru.get(1);lru.set(5,5);lru.get(1);
        lru.dLinkedList.printList(false);
        System.out.print(" | ");
        lru.dLinkedList.printList(true);
    }

    public LRUCache(int capacity) {
        dLinkedList = new DLinkedList();
        dataMap = new HashMap<Integer, DLinkedItem>(capacity);
        this.capacity = capacity;
    }

    public int get(int key) {
        if (dataMap.containsKey(key)) {
            DLinkedItem d = dataMap.get(key);
            dLinkedList.moveToFront(d);
            return d.val;
        }
        else {
            return -1;
        }
    }

    public void set(int key, int value) {
        if (dataMap.containsKey(key)) {
            DLinkedItem d = dataMap.get(key);
            d.val = value;
            dLinkedList.moveToFront(d);
        }
        else {
            if (dataMap.size() < capacity) { // addToFront
                DLinkedItem d = new DLinkedItem(value, key);
                dataMap.put(key, d);
                dLinkedList.addToFront(d);
            }
            else { //
                DLinkedItem d = new DLinkedItem(value, key);
                int rmKey = dLinkedList.removeLeast();
                dataMap.remove(rmKey);
                dataMap.put(key, d);
                dLinkedList.addToFront(d);
            }
        }
    }

    private Map<Integer, DLinkedItem> dataMap;
    private int capacity;
    private DLinkedList dLinkedList;
}