org.neo4j.kernel.impl.cache.LruCache Maven / Gradle / Ivy
/**
* Copyright (c) 2002-2013 "Neo Technology,"
* Network Engine for Objects in Lund AB [http://neotechnology.com]
*
* This file is part of Neo4j.
*
* Neo4j 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.
*
* This program 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 this program. If not, see maxSize set and when the number of cached
* elements exceeds that limit the least recently used element will be removed.
*/
public class LruCache
{
private final String name;
int maxSize = 1000;
private boolean resizing = false;
private boolean adaptive = false;
private final Map cache = new LinkedHashMap( 500, 0.75f, true )
{
@Override
protected boolean removeEldestEntry( Map.Entry eldest )
{
// synchronization miss with old value on maxSize here is ok
if ( super.size() > maxSize )
{
super.remove( eldest.getKey() );
elementCleaned( eldest.getValue() );
}
return false;
}
};
/**
* Creates a LRU cache. If maxSize < 1 an
* IllegalArgumentException is thrown.
*
* @param name
* name of cache
* @param maxSize
* maximum size of this cache
* @param cacheManager
* adaptive cache manager or null if adaptive caching not needed
*/
public LruCache( String name, int maxSize )
{
if ( name == null || maxSize < 1 )
{
throw new IllegalArgumentException( "maxSize=" + maxSize
+ ", name=" + name );
}
this.name = name;
this.maxSize = maxSize;
}
public String getName()
{
return this.name;
}
public synchronized void put( K key, E element )
{
if ( key == null || element == null )
{
throw new IllegalArgumentException( "key=" + key + ", element="
+ element );
}
cache.put( key, element );
}
public synchronized E remove( K key )
{
if ( key == null )
{
throw new IllegalArgumentException( "Null parameter" );
}
return cache.remove( key );
}
public synchronized E get( K key )
{
if ( key == null )
{
throw new IllegalArgumentException();
}
return counter.count( cache.get( key ) );
}
public synchronized void clear()
{
resizeInternal( 0 );
}
public synchronized int size()
{
return cache.size();
}
public synchronized Set keySet()
{
return cache.keySet();
}
public synchronized Collection values()
{
return cache.values();
}
public synchronized Set> entrySet()
{
return cache.entrySet();
}
/**
* Returns the maximum size of this cache.
*
* @return maximum size
*/
public int maxSize()
{
return maxSize;
}
/**
* Changes the max size of the cache. If newMaxSize is
* greater then maxSize() next invoke to maxSize()
* will return newMaxSize and the entries in cache will not
* be modified.
*
* If newMaxSize is less then size()
* the cache will shrink itself removing least recently used element until
* size() equals newMaxSize. For each element
* removed the {@link #elementCleaned} method is invoked.
*
* If newMaxSize is less then 1 an
* {@link IllegalArgumentException} is thrown.
*
* @param newMaxSize
* the new maximum size of the cache
*/
public synchronized void resize( int newMaxSize )
{
if ( newMaxSize < 1 )
{
throw new IllegalArgumentException( "newMaxSize=" + newMaxSize );
}
resizeInternal( newMaxSize );
}
private void resizeInternal( int newMaxSize )
{
resizing = true;
try
{
if ( newMaxSize >= size() )
{
maxSize = newMaxSize;
}
else if ( newMaxSize == 0 )
{
java.util.Iterator> itr = cache.entrySet().iterator();
while ( itr.hasNext())
{
E element = itr.next().getValue();
elementCleaned( element );
}
cache.clear();
}
else
{
maxSize = newMaxSize;
java.util.Iterator> itr = cache.entrySet()
.iterator();
while ( itr.hasNext() && cache.size() > maxSize )
{
E element = itr.next().getValue();
itr.remove();
elementCleaned( element );
}
}
}
finally
{
resizing = false;
}
}
boolean isResizing()
{
return resizing;
}
public void elementCleaned( E element )
{
}
public boolean isAdaptive()
{
return adaptive;
}
public void setAdaptiveStatus( boolean status )
{
this.adaptive = status;
}
public void putAll( Map map )
{
cache.putAll( map );
}
private final HitCounter counter = new HitCounter();
public long hitCount()
{
return counter.getHitsCount();
}
public long missCount()
{
return counter.getMissCount();
}
}