package org.societies.android.platform.context;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Map;
/**
* An LRU cache which stores recently inserted entries and all entries ever
* inserted which still has a strong reference elsewhere.
*/
public class LruCache<K, V> {
private final HashMap<K, V> mLruMap;
private final HashMap<K, Entry<K, V>> mWeakMap =
new HashMap<K, Entry<K, V>>();
private ReferenceQueue<V> mQueue = new ReferenceQueue<V>();
@SuppressWarnings("serial")
public LruCache(final int capacity) {
mLruMap = new LinkedHashMap<K, V>(16, 0.75f, true) {
@Override
protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
return size() > capacity;
}
};
}
private static class Entry<K, V> extends WeakReference<V> {
K mKey;
public Entry(K key, V value, ReferenceQueue<V> queue) {
super(value, queue);
mKey = key;
}
}
@SuppressWarnings("unchecked")
private void cleanUpWeakMap() {
Entry<K, V> entry = (Entry<K, V>) mQueue.poll();
while (entry != null) {
mWeakMap.remove(entry.mKey);
entry = (Entry<K, V>) mQueue.poll();
}
}
public synchronized V put(K key, V value) {
cleanUpWeakMap();
mLruMap.put(key, value);
Entry<K, V> entry = mWeakMap.put(
key, new Entry<K, V>(key, value, mQueue));
return entry == null ? null : entry.get();
}
public synchronized V get(K key) {
cleanUpWeakMap();
V value = mLruMap.get(key);
if (value != null) return value;
Entry<K, V> entry = mWeakMap.get(key);
return entry == null ? null : entry.get();
}
public synchronized void clear() {
mLruMap.clear();
mWeakMap.clear();
mQueue = new ReferenceQueue<V>();
}
}