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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 implements MemoryCacheAware {

	/** Stores not strong references to objects */
	private final Map> softMap = Collections.synchronizedMap(new HashMap>());

	@Override
	public V get(K key) {
		V result = null;
		Reference 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 keys() {
		return softMap.keySet();
	}

	@Override
	public void clear() {
		softMap.clear();
	}

	/** Creates {@linkplain Reference not strong} reference of value */
	protected abstract Reference createReference(V value);
}