/*
* #!
* Ontopia Engine
* #-
* Copyright (C) 2001 - 2013 The Ontopia Project
* #-
* Licensed 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 net.ontopia.utils;
import java.util.Iterator;
import java.util.NoSuchElementException;
/**
* INTERNAL: An iterator that uses a decider to filter the elements of
* another iterator.</p>
*/
public class DeciderIterator<T> implements Iterator<T> {
protected DeciderIF<T> decider;
protected Iterator<T> iterator;
protected boolean done;
protected T next;
public DeciderIterator(DeciderIF<T> decider, Iterator<T> iterator) {
this.decider = decider;
this.iterator = iterator;
// Find the first applicable element.
findNext();
}
protected void findNext() {
// Loop over the remaining elements to find next applicable element.
while (iterator.hasNext()) {
T element = iterator.next();
// Check to see if element is acceptable.
if (decider.ok(element)) {
next = element;
return;
}
}
// There are no more elements and we're done.
done = true;
}
public boolean hasNext() {
// If we're done there are no more elements in this iterator.
if (done) return false;
// We're not done and there are more elements.
return true;
}
public T next() {
// Throw exception if there are no more elements.
if (done) throw new NoSuchElementException();
// Locate next applicable element.
T object = next;
findNext();
// Return element.
return object;
}
public void remove() {
// Delegate remove to underlying iterator.
iterator.remove();
}
}