LRUCache

package tests.sound;

import java.util.Collection;
import java.util.LinkedHashMap;
import java.util.Map;

/**
 * A simple implementation of an LRU cache.
 * <p>
 * Retrieved from <a href=
 * "http://stackoverflow.com/questions/224868/easy-simple-to-use-lru-cache-in-java"
 * >Stackoverflow</a>.
 *
 * @author Gustavo Steigert
 */
public class LRUCache<K, V>
{
    /**
     * Called when a cached element is about to be removed.
     */
    public interface CacheEntryRemovedListener<K, V>
    {
        void notifyEntryRemoved(
            K key,
            V value );
    }

    private Map<K,V> cache;
    private CacheEntryRemovedListener<K,V> entryRemovedListener;

    /**
     * Creates the cache with the specified max entries.
     */
    public LRUCache(
        final int maxEntries )
    {
        cache = new LinkedHashMap<K,V>( maxEntries + 1, .75F, true ) {
            private static final long serialVersionUID = 1L;

            public boolean removeEldestEntry(
                Map.Entry<K,V> eldest )
            {
                if( size() > maxEntries ) {
                    if( entryRemovedListener != null ) {
                        entryRemovedListener.notifyEntryRemoved( eldest.getKey(), eldest.getValue() );
                    }
                    return true;
                }
                return false;
            }
        };
    }

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

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

    public Collection<V> retrieveAll()
    {
        return cache.values();
    }

    public void setEntryRemovedListener(
        CacheEntryRemovedListener<K,V> entryRemovedListener )
    {
        this.entryRemovedListener = entryRemovedListener;
    }
}