LFU(Least Frequently Used) 缓存实现

[XingdiWang]

import java.util.HashMap;
import java.util.Iterator;

public class LFUCache {
    private HashMap<String, Node> cache = null;
    private int capacity = 0;
    private int used = 0;

    public LFUCache(int capacity){
        cache = new HashMap<String,Node>(capacity,0.75f);
        this.capacity = capacity;
    }

    public int get(int key){
        Node node = cache.get(String.valueOf(key));
        if(node == null){
            return -1;
        }
        node.useCount++;
        node.lastGetTime = System.nanoTime();
        return node.value;
    }
    public void set(int key,int value){
        Node n = cache.get(String.valueOf(key));
        if(n != null){
            n.useCount++;
            n.lastGetTime = System.nanoTime();
            n.value = value;
            return;
        }
        else{
            Node node = new Node();
            node.value = value;
            node.useCount = 0;
            node.lastGetTime = System.nanoTime();
            if(this.capacity == 0){
                return;
            }
            if(used<this.capacity){
                used++;
                cache.put(String.valueOf(key),node);
            }else{
                    removeLast();
                    cache.put(String.valueOf(key),node);
                }
            }
    }
    public void removeLast(){
        int minCount = Integer.MAX_VALUE;
        long getTime = System.nanoTime();
        String temp = null;

        Iterator<String> it = cache.keySet().iterator();
        while(it.hasNext()){
            String key = it.next();
             Node node  = cache.get(key);
             if(node.useCount<minCount || (node.useCount == minCount && node.lastGetTime<getTime)){
                 temp = key;
                 minCount = node.useCount;
                 getTime = node.lastGetTime;
             }
        }
        cache.remove(temp);
    }
    public class Node{
        public int value;
        public int useCount;
        public long lastGetTime;
    }
}