    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.collections4.iterators;
    018
    019import java.util.Iterator;
    020
    021import org.apache.commons.collections4.Transformer;
    022
    023/**
    024 * Decorates an iterator such that each element returned is transformed.
    025 *
    026 * @since 1.0
    027 */
    028public class TransformIterator<I, O> implements Iterator<O> {
    029
    030    /** The iterator being used */
    031    private Iterator<? extends I> iterator;
    032    /** The transformer being used */
    033    private Transformer<? super I, ? extends O> transformer;
    034
    035    /**
    036     * Constructs a new {@code TransformIterator} that will not function
    037     * until the {@link #setIterator(Iterator) setIterator} and
    038     * {@link #setTransformer(Transformer)} methods are invoked.
    039     */
    040    public TransformIterator() {
    041    }
    042
    043    /**
    044     * Constructs a new {@code TransformIterator} that won't transform
    045     * elements from the given iterator.
    046     *
    047     * @param iterator  the iterator to use
    048     */
    049    public TransformIterator(final Iterator<? extends I> iterator) {
    050        this.iterator = iterator;
    051    }
    052
    053    /**
    054     * Constructs a new {@code TransformIterator} that will use the
    055     * given iterator and transformer.  If the given transformer is null,
    056     * then objects will not be transformed.
    057     *
    058     * @param iterator  the iterator to use
    059     * @param transformer  the transformer to use
    060     */
    061    public TransformIterator(final Iterator<? extends I> iterator,
    062                             final Transformer<? super I, ? extends O> transformer) {
    063        this.iterator = iterator;
    064        this.transformer = transformer;
    065    }
    066
    067    /**
    068     * Gets the iterator this iterator is using.
    069     *
    070     * @return the iterator.
    071     */
    072    public Iterator<? extends I> getIterator() {
    073        return iterator;
    074    }
    075
    076    /**
    077     * Gets the transformer this iterator is using.
    078     *
    079     * @return the transformer.
    080     */
    081    public Transformer<? super I, ? extends O> getTransformer() {
    082        return transformer;
    083    }
    084
    085    @Override
    086    public boolean hasNext() {
    087        return iterator.hasNext();
    088    }
    089
    090    /**
    091     * Gets the next object from the iteration, transforming it using the
    092     * current transformer. If the transformer is null, no transformation
    093     * occurs and the object from the iterator is returned directly.
    094     *
    095     * @return the next object
    096     * @throws java.util.NoSuchElementException if there are no more elements
    097     */
    098    @Override
    099    public O next() {
    100        return transform(iterator.next());
    101    }
    102
    103    @Override
    104    public void remove() {
    105        iterator.remove();
    106    }
    107
    108    /**
    109     * Sets the iterator for this iterator to use.
    110     * If iteration has started, this effectively resets the iterator.
    111     *
    112     * @param iterator  the iterator to use
    113     */
    114    public void setIterator(final Iterator<? extends I> iterator) {
    115        this.iterator = iterator;
    116    }
    117
    118    /**
    119     * Sets the transformer this the iterator to use.
    120     * A null transformer is a no-op transformer.
    121     *
    122     * @param transformer  the transformer to use
    123     */
    124    public void setTransformer(final Transformer<? super I, ? extends O> transformer) {
    125        this.transformer = transformer;
    126    }
    127
    128    /**
    129     * Transforms the given object using the transformer.
    130     * If the transformer is null, the original object is returned as-is.
    131     *
    132     * @param source  the object to transform
    133     * @return the transformed object
    134     */
    135    protected O transform(final I source) {
    136        return transformer.transform(source);
    137    }
    138}