    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    /**
    037     * Constructs a new <code>TransformIterator</code> that will not function
    038     * until the {@link #setIterator(Iterator) setIterator} and
    039     * {@link #setTransformer(Transformer)} methods are invoked.
    040     */
    041    public TransformIterator() {
    042        super();
    043    }
    044
    045    /**
    046     * Constructs a new <code>TransformIterator</code> that won't transform
    047     * elements from the given iterator.
    048     *
    049     * @param iterator  the iterator to use
    050     */
    051    public TransformIterator(final Iterator<? extends I> iterator) {
    052        super();
    053        this.iterator = iterator;
    054    }
    055
    056    /**
    057     * Constructs a new <code>TransformIterator</code> that will use the
    058     * given iterator and transformer.  If the given transformer is null,
    059     * then objects will not be transformed.
    060     *
    061     * @param iterator  the iterator to use
    062     * @param transformer  the transformer to use
    063     */
    064    public TransformIterator(final Iterator<? extends I> iterator,
    065                             final Transformer<? super I, ? extends O> transformer) {
    066        super();
    067        this.iterator = iterator;
    068        this.transformer = transformer;
    069    }
    070
    071    //-----------------------------------------------------------------------
    072    @Override
    073    public boolean hasNext() {
    074        return iterator.hasNext();
    075    }
    076
    077    /**
    078     * Gets the next object from the iteration, transforming it using the
    079     * current transformer. If the transformer is null, no transformation
    080     * occurs and the object from the iterator is returned directly.
    081     *
    082     * @return the next object
    083     * @throws java.util.NoSuchElementException if there are no more elements
    084     */
    085    @Override
    086    public O next() {
    087        return transform(iterator.next());
    088    }
    089
    090    @Override
    091    public void remove() {
    092        iterator.remove();
    093    }
    094
    095    //-----------------------------------------------------------------------
    096    /**
    097     * Gets the iterator this iterator is using.
    098     *
    099     * @return the iterator.
    100     */
    101    public Iterator<? extends I> getIterator() {
    102        return iterator;
    103    }
    104
    105    /**
    106     * Sets the iterator for this iterator to use.
    107     * If iteration has started, this effectively resets the iterator.
    108     *
    109     * @param iterator  the iterator to use
    110     */
    111    public void setIterator(final Iterator<? extends I> iterator) {
    112        this.iterator = iterator;
    113    }
    114
    115    //-----------------------------------------------------------------------
    116    /**
    117     * Gets the transformer this iterator is using.
    118     *
    119     * @return the transformer.
    120     */
    121    public Transformer<? super I, ? extends O> getTransformer() {
    122        return transformer;
    123    }
    124
    125    /**
    126     * Sets the transformer this the iterator to use.
    127     * A null transformer is a no-op transformer.
    128     *
    129     * @param transformer  the transformer to use
    130     */
    131    public void setTransformer(final Transformer<? super I, ? extends O> transformer) {
    132        this.transformer = transformer;
    133    }
    134
    135    //-----------------------------------------------------------------------
    136    /**
    137     * Transforms the given object using the transformer.
    138     * If the transformer is null, the original object is returned as-is.
    139     *
    140     * @param source  the object to transform
    141     * @return the transformed object
    142     */
    143    protected O transform(final I source) {
    144        return transformer.transform(source);
    145    }
    146}