| /* |
| * 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.commons.collections4.iterators; |
| |
| import java.util.Iterator; |
| import java.util.NoSuchElementException; |
| |
| import org.apache.commons.collections4.Predicate; |
| |
| /** |
| * Decorates another {@link Iterator} using a predicate to filter elements. |
| * <p> |
| * This iterator decorates the underlying iterator, only allowing through |
| * those elements that match the specified {@link Predicate Predicate}. |
| * |
| * @param <E> the type of elements returned by this iterator. |
| * @since 1.0 |
| */ |
| public class FilterIterator<E> implements Iterator<E> { |
| |
| /** The iterator being used */ |
| private Iterator<? extends E> iterator; |
| /** The predicate being used */ |
| private Predicate<? super E> predicate; |
| /** The next object in the iteration */ |
| private E nextObject; |
| /** Whether the next object has been calculated yet */ |
| private boolean nextObjectSet; |
| |
| //----------------------------------------------------------------------- |
| /** |
| * Constructs a new {@code FilterIterator} that will not function |
| * until {@link #setIterator(Iterator) setIterator} is invoked. |
| */ |
| public FilterIterator() { |
| } |
| |
| /** |
| * Constructs a new {@code FilterIterator} that will not function |
| * until {@link #setPredicate(Predicate) setPredicate} is invoked. |
| * |
| * @param iterator the iterator to use |
| */ |
| public FilterIterator(final Iterator<? extends E> iterator) { |
| this.iterator = iterator; |
| } |
| |
| /** |
| * Constructs a new {@code FilterIterator} that will use the |
| * given iterator and predicate. |
| * |
| * @param iterator the iterator to use |
| * @param predicate the predicate to use |
| */ |
| public FilterIterator(final Iterator<? extends E> iterator, final Predicate<? super E> predicate) { |
| 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 |
| * @throws NullPointerException if either the iterator or predicate are null |
| */ |
| @Override |
| public boolean hasNext() { |
| return nextObjectSet || setNextObject(); |
| } |
| |
| /** |
| * Returns the next object that matches the predicate. |
| * |
| * @return the next object which matches the given predicate |
| * @throws NullPointerException if either the iterator or predicate are null |
| * @throws NoSuchElementException if there are no more elements that |
| * match the predicate |
| */ |
| @Override |
| public E next() { |
| if (!nextObjectSet && !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()} was called, but not after |
| * {@code hasNext()}, because the {@code hasNext()} call |
| * changes the base iterator. |
| * |
| * @throws IllegalStateException if {@code hasNext()} has already |
| * been called. |
| */ |
| @Override |
| 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<? extends E> 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(final Iterator<? extends E> iterator) { |
| this.iterator = iterator; |
| nextObject = null; |
| nextObjectSet = false; |
| } |
| |
| //----------------------------------------------------------------------- |
| /** |
| * Gets the predicate this iterator is using. |
| * |
| * @return the predicate |
| */ |
| public Predicate<? super E> getPredicate() { |
| return predicate; |
| } |
| |
| /** |
| * Sets the predicate this the iterator to use. |
| * |
| * @param predicate the predicate to use |
| */ |
| public void setPredicate(final Predicate<? super E> predicate) { |
| this.predicate = predicate; |
| nextObject = null; |
| nextObjectSet = false; |
| } |
| |
| //----------------------------------------------------------------------- |
| /** |
| * Set nextObject to the next object. If there are no more |
| * objects then return false. Otherwise, return true. |
| */ |
| private boolean setNextObject() { |
| while (iterator.hasNext()) { |
| final E object = iterator.next(); |
| if (predicate.evaluate(object)) { |
| nextObject = object; |
| nextObjectSet = true; |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| } |