Java实现LRU缓存的实例详解

void afterNodeAccess(Node<K,V> e) { // move node to last
  LinkedHashMap.Entry<K,V> last;
  if (accessOrder && (last = tail) != e) {
    LinkedHashMap.Entry<K,V> p =
      (LinkedHashMap.Entry<K,V>)e, b = p.before, a = p.after;
    p.after = null;
    if (b == null)
      head = a;
    else
      b.after = a;
    if (a != null)
      a.before = b;
    else
      last = b;
    if (last == null)
      head = p;
    else {
      p.before = last;
      last.after = p;
    }
    tail = p;
    ++modCount;
  }
}

void afterNodeInsertion(boolean evict) { // possibly remove eldest
  LinkedHashMap.Entry<K,V> first;
  if (evict && (first = head) != null && removeEldestEntry(first)) {
    K key = first.key;
    removeNode(hash(key), key, null, false, true);
  }
} 

@Override
public boolean removeEldestEntry(Map.Entry<K, V> eldest){   
  return size()>capacity;    
}

import java.util.Set;

 import com.googlecode.concurrentlinkedhashmap.Weighers;
 import com.googlecode.concurrentlinkedhashmap.ConcurrentLinkedHashMap;
 public class ConcurrentLRUCache<K, V> {
   public static final int           DEFAULT_CONCURENCY_LEVEL = 32;

 private final ConcurrentLinkedHashMap<K, V> map;


 public ConcurrentLRUCache(int capacity) {
   this(capacity, DEFAULT_CONCURENCY_LEVEL);
 }

 public ConcurrentLRUCache(int capacity, int concurrency) {
   map = new ConcurrentLinkedHashMap.Builder<K, V>().weigher(Weighers.<V> singleton())
    .initialCapacity(capacity).maximumWeightedCapacity(capacity)
    .concurrencyLevel(concurrency).build();
 }

 public void put(K key, V value) {
   map.put(key, value);
 }

 public V get(K key) {
   V v = map.get(key);
   return v;
 }

 public V getInternal(K key) {
   return map.get(key);
 }

 public void remove(K key) {
   map.remove(key);
 }

 public long getCapacity() {
   return map.capacity();
 }


 public void updateCapacity(int capacity) {
   map.setCapacity(capacity);
 }


 public int getSize() {
   return map.size();
 }


 public void clear() {
   map.clear();
 }

 public Set<K> getKeySet() {
   return map.keySet();
 }
}