AccessBasedLRUCache.java

/*******************************************************************************
 * Copyright (c) 2013 Obeo.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 *     Obeo - initial API and implementation
 *******************************************************************************/
package org.eclipse.emf.compare.match.eobject.internal;

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

/**
 * A Map acting like a LRU cache which will evict elements which have not been accessed in a while.
 * 
 * @param <K>
 *            the type of keys maintained by this map
 * @param <V>
 *            the type of mapped values
 * @author <a href="mailto:cedric.brun@obeo.fr">Cedric Brun</a>
 */
public class AccessBasedLRUCache<K, V> extends LinkedHashMap<K, V> {

	/**
	 * serialversion uid.
	 */
	private static final long serialVersionUID = 1L;

	/**
	 * The maximum size of the cache before it starts evicting elements.
	 */
	private int maxSize;

	/**
	 * Create a new cache.
	 * 
	 * @param maxSize
	 *            the maximum size of the cache before it starts evicting elements.
	 * @param initialCapacity
	 *            pre-allocated capacity for the cache.
	 * @param loadFactor
	 *            the load factor
	 */
	public AccessBasedLRUCache(int maxSize, int initialCapacity, float loadFactor) {
		super(initialCapacity, loadFactor, true);
		this.maxSize = maxSize;
	}

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