LRU缓存简单实现

缓存接口定义

/*** 缓存接口* * @author zhi**/
public interface ICache<K, V> {/*** 添加缓存数据* * @param key* @param value*/void put(K key, V value);/*** 获取缓存数据* * @param key* @return*/V get(K key);/*** 删除缓存数据* * @param key* @return*/V remove(K key);/*** 清除缓存*/void clear();
}

利用LinkedHashMap实现

import java.util.LinkedHashMap;
import java.util.Map;public class LRUCache<K, V> implements ICache<K, V> {private Map<K, V> map = null;@SuppressWarnings("serial")public LRUCache(final int maxCapacity) {map = new LinkedHashMap<K, V>(maxCapacity, 0.75f, true) {@Overrideprotected boolean removeEldestEntry(java.util.Map.Entry<K, V> eldest) {return size() > maxCapacity;}};}@Overridepublic V get(K key) {return map.get(key);}@Overridepublic synchronized void put(K key, V value) {map.put(key, value);}@Overridepublic V remove(K key) {return map.remove(key);}@Overridepublic void clear() {map.clear();}
}

 利用双链表实现

import java.util.HashMap;public class LRUCache<K, V> implements ICache<K, V> {private final int maxCapacity;private CacheItem first;private CacheItem last;private HashMap<K, CacheItem> cache;public LRUCache(final int maxCapacity) {this.maxCapacity = maxCapacity;cache = new HashMap<K, CacheItem>(maxCapacity);}@Overridepublic V get(K key) {CacheItem item = cache.get(key);if (item == null) {return null;}moveToFirst(item);return item.value;}@Overridepublic synchronized void put(K key, V value) {CacheItem item = cache.get(key);if (item != null) {item.value = value;moveToFirst(item);} else {if (cache.size() == maxCapacity) {cache.remove(last.key);last = last.pre;if (last == null) {first = null;} else {last.next = null;}}item = new CacheItem(key, value);cache.put(key, item);if (first != null) {item.next = first;first.pre = item;}first = item;if (last == null) {last = item;}}}@Overridepublic V remove(K key) {if (cache.containsKey(key)) {CacheItem item = cache.get(key);if (item.pre != null) {item.pre.next = item.next;}if (item.next != null) {item.next.pre = item.pre;}if (item == first) {first = item.next;}if (item == last) {last = item.pre;}return cache.remove(key).value;} else {return null;}}private void moveToFirst(CacheItem item) {if (item == first) {return;}if (item.next == null) {last = item.pre;}item.pre.next = item.next;item.next = first;first = item;first.pre = null;}@Overridepublic void clear() {first = last = null;cache.clear();}class CacheItem {CacheItem pre;CacheItem next;K key;V value;public CacheItem(K key, V value) {this.key = key;this.value = value;}}
}