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() );
}
}