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.apply(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}