package com.nostra13.universalimageloader.cache.memory;



import java.lang.ref.Reference;

import java.util.Collection;

import java.util.Collections;

import java.util.HashMap;

import java.util.Map;



/**

 * Base memory cache. Implements common functionality for memory cache. Provides object references (

 * {@linkplain Reference not strong}) storing.

 * 

 * @author Sergey Tarasevich (nostra13[at]gmail[dot]com)

 */

public abstract class BaseMemoryCache<K, V> implements MemoryCacheAware<K, V> {



	/** Stores not strong references to objects */

	private final Map<K, Reference<V>> softMap = Collections.synchronizedMap(new HashMap<K, Reference<V>>());



	@Override

	public V get(K key) {

		V result = null;

		Reference<V> reference = softMap.get(key);

		if (reference != null) {

			result = reference.get();

		}

		return result;

	}



	@Override

	public boolean put(K key, V value) {

		softMap.put(key, createReference(value));

		return true;

	}



	@Override

	public void remove(K key) {

		softMap.remove(key);

	}



	@Override

	public Collection<K> keys() {

		return softMap.keySet();

	}



	@Override

	public void clear() {

		softMap.clear();

	}



	/** Creates {@linkplain Reference not strong} reference of value */

	protected abstract Reference<V> createReference(V value);

}