/**
* Copyright (c) 2002-2011 "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 Affero 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.neo4j.helpers.collection;
import java.util.Iterator;
import org.neo4j.helpers.Predicate;
/**
* An iterator which filters another iterator, only letting items with certain
* criterias pass through. All iteration/filtering is done lazily.
*
* @param <T> the type of items in the iteration.
*/
public class FilteringIterator<T> extends PrefetchingIterator<T>
{
private final Iterator<T> source;
private final Predicate<T> predicate;
public FilteringIterator( Iterator<T> source, Predicate<T> predicate )
{
this.source = source;
this.predicate = predicate;
}
@Override
protected T fetchNextOrNull()
{
while ( source.hasNext() )
{
T testItem = source.next();
if ( predicate.accept( testItem ) )
{
return testItem;
}
}
return null;
}
public static <T> Iterator<T> notNull( Iterator<T> source )
{
return new FilteringIterator<T>( source, FilteringIterable.<T>notNullPredicate() );
}
public static <T> Iterator<T> noDuplicates( Iterator<T> source )
{
return new FilteringIterator<T>( source, FilteringIterable.<T>noDuplicatesPredicate() );
}
}