LRUCache

MyLRUCache 缓存类

package org.jf.alg.lru;

import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;


/**
 * 限定容量二叉堆+HashMap实现LRU
 * 
 * @author junfeng.chen
 *
 */
public class MyLRUCache {
		
	private Map<Object,ValueEntry> container = Collections.synchronizedMap( new HashMap<Object,ValueEntry>());
	
	private List<Object> visistList = Collections.synchronizedList(new LinkedList<Object>());//key值的访问历史
	
	private KeyVisitCounter[] heap_array ;
	
	private int increaseStep = 500 ;
	
	private int initSize = 2000;
	
//访问记录列表  每次访问元素，将其访问记录放入列表，并有后台线程处理
	private long reset_interval = 2000*60;//刷新时间默认为2分钟
	
	private int capacity = 100000;
	
	private int size = 0;
	
	private boolean bln_started = false;
	
	private PerlocateThread perlocateThd ;
	
	public MyLRUCache()
	{
		init();
	}
	
	public MyLRUCache(int capacity)
	{
		this.capacity = capacity;
		init();
	}
	
	/**
	 * 
	 * @param capacity 最大容量
	 * @param time_cycle 计数时间周期
	 */
	public MyLRUCache(int capacity,int time_cycle)
	{
		this.capacity = capacity;
		this.reset_interval = time_cycle;
		init();
	}
	
	public void start()
	{
		this.perlocateThd = new PerlocateThread();
		perlocateThd.start();
		this.bln_started = true;
	}
	
	public void stop()
	{
		if(perlocateThd != null)
			perlocateThd.exit();
		this.bln_started = false;
		this.heap_array = new KeyVisitCounter[this.initSize+1];
		this.visistList.clear();
		this.container.clear();
	}
	private void init()
	{
		this.heap_array = new KeyVisitCounter[this.initSize+1];
	}
	
	public void resetCount()
	{
		for(KeyVisitCounter counter:heap_array)
		{
			if(counter != null)
				counter.reSet();
			else
				 break;
		}
	}
	
	
//	public void remove(Object key)
//	{
//		not support remove explicity
//	}
//	
	public Object get(Object key)
	{
		assertStatus();
		ValueEntry valueEntry = this.container.get(key);
		if(valueEntry != null)
		{
			//在堆中查找当前key，并对其count加1
			visistList.add(key);
			return valueEntry.getData();
		}
		return null;
	}
	
	public void put(Object key,Object value)
	{
		assertStatus();
		ValueEntry entry = new ValueEntry(value);
		this.visistList.add(key);
		this.container.put(key, entry);//实际上 保存的元素可能比capacity多
	}
	
	public int getSize()
	{
		return this.size;
	}
	
	
	/***********************some help methods****************************************************/
	
	private void assertStatus()
	{
		if(!this.bln_started)
			throw new RuntimeException("Illegle Cache Staus,not started");
	}

	/**
	 * 
	 * @param key
	 * @return 该key值对应的索引
	 */
	private int  perlocateUp(Object key/* , ValueEntry entry*/)
	{
		int indx = -1;
		ValueEntry entry = container.get(key);
		if(entry.getKeyIndx()==-1)
		{
			if(size<this.capacity&&size==this.heap_array.length-1)
			{
				int step = this.capacity - this.size;
				step = step<=this.increaseStep?step:increaseStep;
				KeyVisitCounter []newArray = new KeyVisitCounter[heap_array.length+step];
				System.arraycopy(heap_array, 1, newArray,1, size);
				heap_array = newArray;
			}
			
			KeyVisitCounter key_counter = new KeyVisitCounter(key);
			key_counter.visit();//缓存已满时，防止最后一个元素总是被删除 刚插入的元素给予特殊待遇
			//新加入一个记录值
			if(this.size==this.capacity)//heap满
			{
				if(heap_array[size].compareTo(key_counter)<=0)
				{
					heap_array[size] = key_counter;
					indx = size;
				}//else indx = -1
				
			}else
			{
				heap_array[size+1] = key_counter;
				indx = size+1;
				size++;
			}
			entry.setKeyIndex(indx);
		}
		else
		{
			indx = entry.getKeyIndx();
		}
		
		if(indx == -1)//
			return -1;
		
		//fix up heap_array to ensure it's heap character
			int parent = indx/2;
			KeyVisitCounter counter = this.heap_array[indx];
			counter.visit();
			while(parent!=0)
			{
				if(this.heap_array[indx].compareTo(this.heap_array[parent])>0)
				{				
					KeyVisitCounter tmp = heap_array[indx];
					heap_array[indx] = heap_array[parent];
					heap_array[parent] = tmp;
					indx = parent;
					
					
					//设置key对应的索引
					this.container.get(heap_array[indx].getKey()).setKeyIndex(indx);
					this.container.get(heap_array[parent].getKey()).setKeyIndex(parent);
					
					parent = indx/2;
				}else
				{
					break;
				}
			}
					
	  return indx;
	}
	
	

	private class PerlocateThread extends Thread
	{
		boolean run = true;
		public void run()
		{
			int count = 200;
			long last_reset_time = System.currentTimeMillis();
			while(run)
			{
				while(count>0&&visistList.size()>0)
				{
					Object key = visistList.remove(0);
					int indx = perlocateUp(key);
					if(indx == -1)
						container.remove(key);
				}
				
				if(System.currentTimeMillis() - last_reset_time >reset_interval)
				{
					resetCount();
					last_reset_time = System.currentTimeMillis();
				}
				try {
					this.sleep(500);
				} catch (InterruptedException e) {
					e.printStackTrace();
					break;
				}	
			}
		}
		
		public void exit()
		{
			run = false;
		}
		
	}
}

访问次数记录类

package org.jf.alg.lru;

public class KeyVisitCounter implements Comparable{

	private Object key;
	private int count;
	
	public KeyVisitCounter(Object key)
	{
		this.key = key;
	}
	
	public void visit()
	{
		count++;
	}
	
	public void visit(int times)
	{
		this.count += times ;
	}
	
	public int getVisitTimes()
	{
		return count;
	}
	
	public Object getKey()
	{
		return this.key;
	}

	public void reSet()
	{
		this.count = 0;
	}
	
	@Override
	public int compareTo(Object o) 
	{

		if(!(o instanceof KeyVisitCounter))
			return 1;
		KeyVisitCounter counter = (KeyVisitCounter) o;
		if(this.count > counter.count)
			return 1;
		if(this.count == counter.count)
			return 0;
		return -1;

	}
}

package org.jf.alg.lru;

public class ValueEntry {

	private int keyIndx = -1;//key在heap数组中的下标
	private Object data;
	
	public ValueEntry(Object data)
	{
		this.data = data;
	}
	
	public Object getData()
	{
		return this.data;
	}
	
	public void setKeyIndex(int indx)
	{
		this.keyIndx = indx;
	}
	
	public int getKeyIndx()
	{
		return this.keyIndx;
	}
}