/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.jena.util.iterator;
import java.util.*;
/**
A MapFilterIterator takes a MapFilter and an [Extended]Iterator and returns a new
ExtendedIterator which delivers the sequence of all non-null elements MapFilter(X)
for X from the base iterator.
*/
public class MapFilterIterator<T,X> extends NiceIterator<X> implements ExtendedIterator<X>
{
MapFilter<T,X> f;
X current;
boolean dead;
ClosableIterator<T> underlying;
/** Creates a sub-Iterator.
* @param fl An object is included if it is accepted by this Filter.
* @param e The parent Iterator.
*/
public MapFilterIterator( MapFilter<T,X> fl, ExtendedIterator<T> e) {
f = fl;
current = null;
dead = false;
underlying = e;
}
/** Are there any more acceptable objects.
* @return true if there is another acceptable object.
*/
@Override
synchronized public boolean hasNext() {
if (current!=null)
return true;
while ( underlying.hasNext() ) {
current = f.accept( underlying.next() );
if (current != null)
return true;
}
current = null;
dead = true;
return false;
}
@Override
public void close()
{
underlying.close();
}
/** remove's the member from the underlying <CODE>Iterator</CODE>;
<CODE>hasNext()</CODE> may not be called between calls to
<CODE>next()</CODE> and <CODE>remove()</CODE>.
*/
@Override
synchronized public void remove() {
if ( current != null || dead )
throw new IllegalStateException(
"FilterIterator does not permit calls to hasNext between calls to next and remove.");
underlying.remove();
}
/** The next acceptable object in the iterator.
* @return The next acceptable object.
*/
@Override
synchronized public X next() {
if (hasNext()) {
X r = current;
current = null;
return r;
}
throw new NoSuchElementException();
}
}