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/*
This file is part of Subsonic.
Subsonic is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Subsonic is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with Subsonic. If not, see <http://www.gnu.org/licenses/>.
Copyright 2009 (C) Sindre Mehus
*/
package net.sourceforge.subsonic.androidapp.util;
import java.lang.ref.SoftReference;
import java.util.HashMap;
import java.util.Map;
/**
* @author Sindre Mehus
*/
public class LRUCache<K,V>{
private final int capacity;
private final Map<K, TimestampedValue> map;
public LRUCache(int capacity) {
map = new HashMap<K, TimestampedValue>(capacity);
this.capacity = capacity;
}
public synchronized V get(K key) {
TimestampedValue value = map.get(key);
V result = null;
if (value != null) {
value.updateTimestamp();
result = value.getValue();
}
return result;
}
public synchronized void put(K key, V value) {
if (map.size() >= capacity) {
removeOldest();
}
map.put(key, new TimestampedValue(value));
}
public void clear() {
map.clear();
}
private void removeOldest() {
K oldestKey = null;
long oldestTimestamp = Long.MAX_VALUE;
for (Map.Entry<K, TimestampedValue> entry : map.entrySet()) {
K key = entry.getKey();
TimestampedValue value = entry.getValue();
if (value.getTimestamp() < oldestTimestamp) {
oldestTimestamp = value.getTimestamp();
oldestKey = key;
}
}
if (oldestKey != null) {
map.remove(oldestKey);
}
}
private final class TimestampedValue {
private final SoftReference<V> value;
private long timestamp;
public TimestampedValue(V value) {
this.value = new SoftReference<V>(value);
updateTimestamp();
}
public V getValue() {
return value.get();
}
public long getTimestamp() {
return timestamp;
}
public void updateTimestamp() {
timestamp = System.currentTimeMillis();
}
}
}
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