    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.bag;
    018
    019import java.util.Set;
    020
    021import org.apache.commons.collections4.Bag;
    022import org.apache.commons.collections4.Transformer;
    023import org.apache.commons.collections4.collection.TransformedCollection;
    024import org.apache.commons.collections4.set.TransformedSet;
    025
    026/**
    027 * Decorates another {@link Bag} to transform objects that are added.
    028 * <p>
    029 * The add methods are affected by this class.
    030 * Thus objects must be removed or searched for using their transformed form.
    031 * For example, if the transformation converts Strings to Integers, you must
    032 * use the Integer form to remove objects.
    033 * </p>
    034 * <p>
    035 * This class is Serializable from Commons Collections 3.1.
    036 * </p>
    037 *
    038 * @param <E> the type of elements in this bag
    039 * @since 3.0
    040 */
    041public class TransformedBag<E> extends TransformedCollection<E> implements Bag<E> {
    042
    043    /** Serialization version */
    044    private static final long serialVersionUID = 5421170911299074185L;
    045
    046    /**
    047     * Factory method to create a transforming bag that will transform
    048     * existing contents of the specified bag.
    049     * <p>
    050     * If there are any elements already in the bag being decorated, they
    051     * will be transformed by this method.
    052     * Contrast this with {@link #transformingBag(Bag, Transformer)}.
    053     *
    054     * @param <E> the type of the elements in the bag
    055     * @param bag  the bag to decorate, must not be null
    056     * @param transformer  the transformer to use for conversion, must not be null
    057     * @return a new transformed Bag
    058     * @throws NullPointerException if bag or transformer is null
    059     * @since 4.0
    060     */
    061    public static <E> Bag<E> transformedBag(final Bag<E> bag, final Transformer<? super E, ? extends E> transformer) {
    062        final TransformedBag<E> decorated = new TransformedBag<>(bag, transformer);
    063        if (!bag.isEmpty()) {
    064            @SuppressWarnings("unchecked") // Bag is of type E
    065            final E[] values = (E[]) bag.toArray(); // NOPMD - false positive for generics
    066            bag.clear();
    067            for (final E value : values) {
    068                decorated.decorated().add(transformer.transform(value));
    069            }
    070        }
    071        return decorated;
    072    }
    073
    074    /**
    075     * Factory method to create a transforming bag.
    076     * <p>
    077     * If there are any elements already in the bag being decorated, they
    078     * are NOT transformed. Contrast this with {@link #transformedBag(Bag, Transformer)}.
    079     *
    080     * @param <E> the type of the elements in the bag
    081     * @param bag  the bag to decorate, must not be null
    082     * @param transformer  the transformer to use for conversion, must not be null
    083     * @return a new transformed Bag
    084     * @throws NullPointerException if bag or transformer is null
    085     * @since 4.0
    086     */
    087    public static <E> Bag<E> transformingBag(final Bag<E> bag, final Transformer<? super E, ? extends E> transformer) {
    088        return new TransformedBag<>(bag, transformer);
    089    }
    090
    091    /**
    092     * Constructor that wraps (not copies).
    093     * <p>
    094     * If there are any elements already in the bag being decorated, they
    095     * are NOT transformed.
    096     *
    097     * @param bag  the bag to decorate, must not be null
    098     * @param transformer  the transformer to use for conversion, must not be null
    099     * @throws NullPointerException if bag or transformer is null
    100     */
    101    protected TransformedBag(final Bag<E> bag, final Transformer<? super E, ? extends E> transformer) {
    102        super(bag, transformer);
    103    }
    104
    105    @Override
    106    public boolean add(final E object, final int nCopies) {
    107        return getBag().add(transform(object), nCopies);
    108    }
    109
    110    @Override
    111    public boolean equals(final Object object) {
    112        return object == this || decorated().equals(object);
    113    }
    114
    115    /**
    116     * Gets the decorated bag.
    117     *
    118     * @return the decorated bag
    119     */
    120    protected Bag<E> getBag() {
    121        return (Bag<E>) decorated();
    122    }
    123
    124    @Override
    125    public int getCount(final Object object) {
    126        return getBag().getCount(object);
    127    }
    128
    129    @Override
    130    public int hashCode() {
    131        return decorated().hashCode();
    132    }
    133
    134    @Override
    135    public boolean remove(final Object object, final int nCopies) {
    136        return getBag().remove(object, nCopies);
    137    }
    138
    139    @Override
    140    public Set<E> uniqueSet() {
    141        final Set<E> set = getBag().uniqueSet();
    142        return TransformedSet.<E>transformingSet(set, transformer);
    143    }
    144
    145}