- /*
- * Copyright 1999-2004 The Apache Software Foundation
- *
- * 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 org.apache.commons.collections.iterators;
-
- import java.util.Iterator;
- import java.util.NoSuchElementException;
-
- import org.apache.commons.collections.Predicate;
-
- /**
- * Decorates an iterator such that only elements matching a predicate filter
- * are returned.
- *
- * @since Commons Collections 1.0
- * @version $Revision: 1.8 $ $Date: 2004/02/18 00:59:50 $
- *
- * @author James Strachan
- * @author Jan Sorensen
- * @author Ralph Wagner
- * @author Stephen Colebourne
- */
- public class FilterIterator implements Iterator {
-
- /** The iterator being used */
- private Iterator iterator;
- /** The predicate being used */
- private Predicate predicate;
- /** The next object in the iteration */
- private Object nextObject;
- /** Whether the next object has been calculated yet */
- private boolean nextObjectSet = false;
-
- //-----------------------------------------------------------------------
- /**
- * Constructs a new <code>FilterIterator</code> that will not function
- * until {@link #setIterator(Iterator) setIterator} is invoked.
- */
- public FilterIterator() {
- super();
- }
-
- /**
- * Constructs a new <code>FilterIterator</code> that will not function
- * until {@link #setPredicate(Predicate) setPredicate} is invoked.
- *
- * @param iterator the iterator to use
- */
- public FilterIterator(Iterator iterator) {
- super();
- this.iterator = iterator;
- }
-
- /**
- * Constructs a new <code>FilterIterator</code> that will use the
- * given iterator and predicate.
- *
- * @param iterator the iterator to use
- * @param predicate the predicate to use
- */
- public FilterIterator(Iterator iterator, Predicate predicate) {
- super();
- this.iterator = iterator;
- this.predicate = predicate;
- }
-
- //-----------------------------------------------------------------------
- /**
- * Returns true if the underlying iterator contains an object that
- * matches the predicate.
- *
- * @return true if there is another object that matches the predicate
- */
- public boolean hasNext() {
- if (nextObjectSet) {
- return true;
- } else {
- return setNextObject();
- }
- }
-
- /**
- * Returns the next object that matches the predicate.
- *
- * @return the next object which matches the given predicate
- * @throws NoSuchElementException if there are no more elements that
- * match the predicate
- */
- public Object next() {
- if (!nextObjectSet) {
- if (!setNextObject()) {
- throw new NoSuchElementException();
- }
- }
- nextObjectSet = false;
- return nextObject;
- }
-
- /**
- * Removes from the underlying collection of the base iterator the last
- * element returned by this iterator.
- * This method can only be called
- * if <code>next()</code> was called, but not after
- * <code>hasNext()</code>, because the <code>hasNext()</code> call
- * changes the base iterator.
- *
- * @throws IllegalStateException if <code>hasNext()</code> has already
- * been called.
- */
- public void remove() {
- if (nextObjectSet) {
- throw new IllegalStateException("remove() cannot be called");
- }
- iterator.remove();
- }
-
- //-----------------------------------------------------------------------
- /**
- * Gets the iterator this iterator is using.
- *
- * @return the iterator.
- */
- public Iterator getIterator() {
- return iterator;
- }
-
- /**
- * Sets the iterator for this iterator to use.
- * If iteration has started, this effectively resets the iterator.
- *
- * @param iterator the iterator to use
- */
- public void setIterator(Iterator iterator) {
- this.iterator = iterator;
- }
-
- //-----------------------------------------------------------------------
- /**
- * Gets the predicate this iterator is using.
- *
- * @return the predicate.
- */
- public Predicate getPredicate() {
- return predicate;
- }
-
- /**
- * Sets the predicate this the iterator to use.
- *
- * @param predicate the transformer to use
- */
- public void setPredicate(Predicate predicate) {
- this.predicate = predicate;
- }
-
- //-----------------------------------------------------------------------
- /**
- * Set nextObject to the next object. If there are no more
- * objects then return false. Otherwise, return true.
- */
- private boolean setNextObject() {
- while (iterator.hasNext()) {
- Object object = iterator.next();
- if (predicate.evaluate(object)) {
- nextObject = object;
- nextObjectSet = true;
- return true;
- }
- }
- return false;
- }
- }