/*
* 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.atlas.iterator;
import java.util.Iterator ;
import java.util.NoSuchElementException ;
import org.apache.jena.atlas.lib.Closeable ;
import org.apache.jena.atlas.lib.Lib ;
public abstract class RepeatApplyIterator<T> implements Iterator<T>, Closeable
{
private Iterator<T> input ;
private boolean finished = false ;
private Iterator<T> currentStage = null ;
protected RepeatApplyIterator(Iterator<T> input)
{
this.input = input ;
}
@Override
public boolean hasNext()
{
if ( finished )
return false ;
for ( ;; )
{
if ( currentStage == null && input.hasNext() )
{
T nextItem = input.next();
currentStage = makeNextStage(nextItem) ;
}
if ( currentStage == null )
{
hasFinished() ;
finished = true ;
return false ;
}
if ( currentStage.hasNext() )
return true ;
currentStage = null ;
}
}
protected abstract Iterator<T> makeNextStage(T t) ;
protected void hasFinished() {}
@Override
public T next()
{
if ( ! hasNext() )
throw new NoSuchElementException(Lib.className(this)+".next()/finished") ;
return currentStage.next() ;
}
@Override
public final void remove()
{ throw new UnsupportedOperationException() ; }
@Override
public void close()
{
Iter.close(input) ;
}
}