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.set;
018
019import java.util.Set;
020
021import org.apache.commons.collections4.Transformer;
022import org.apache.commons.collections4.collection.TransformedCollection;
023
024/**
025 * Decorates another {@code Set} to transform objects that are added.
026 * <p>
027 * The add methods are affected by this class.
028 * Thus objects must be removed or searched for using their transformed form.
029 * For example, if the transformation converts Strings to Integers, you must
030 * use the Integer form to remove objects.
031 * </p>
032 * <p>
033 * This class is Serializable from Commons Collections 3.1.
034 * </p>
035 *
036 * @param <E> the type of the elements in this set
037 * @since 3.0
038 */
039public class TransformedSet<E> extends TransformedCollection<E> implements Set<E> {
040
041    /** Serialization version */
042    private static final long serialVersionUID = 306127383500410386L;
043
044    /**
045     * Factory method to create a transforming set that will transform
046     * existing contents of the specified set.
047     * <p>
048     * If there are any elements already in the set being decorated, they
049     * will be transformed by this method.
050     * Contrast this with {@link #transformingSet(Set, Transformer)}.
051     *
052     * @param <E> the element type
053     * @param set  the set to decorate, must not be null
054     * @param transformer  the transformer to use for conversion, must not be null
055     * @return a new transformed set
056     * @throws NullPointerException if set or transformer is null
057     * @since 4.0
058     */
059    public static <E> Set<E> transformedSet(final Set<E> set, final Transformer<? super E, ? extends E> transformer) {
060        final TransformedSet<E> decorated = new TransformedSet<>(set, transformer);
061        if (!set.isEmpty()) {
062            @SuppressWarnings("unchecked") // set is type E
063            final E[] values = (E[]) set.toArray(); // NOPMD - false positive for generics
064            set.clear();
065            for (final E value : values) {
066                decorated.decorated().add(transformer.apply(value));
067            }
068        }
069        return decorated;
070    }
071
072    /**
073     * Factory method to create a transforming set.
074     * <p>
075     * If there are any elements already in the set being decorated, they
076     * are NOT transformed.
077     * Contrast this with {@link #transformedSet(Set, Transformer)}.
078     *
079     * @param <E> the element type
080     * @param set  the set to decorate, must not be null
081     * @param transformer  the transformer to use for conversion, must not be null
082     * @return a new transformed set
083     * @throws NullPointerException if set or transformer is null
084     * @since 4.0
085     */
086    public static <E> TransformedSet<E> transformingSet(final Set<E> set,
087            final Transformer<? super E, ? extends E> transformer) {
088        return new TransformedSet<>(set, transformer);
089    }
090
091    /**
092     * Constructor that wraps (not copies).
093     * <p>
094     * If there are any elements already in the set being decorated, they
095     * are NOT transformed.
096     *
097     * @param set  the set to decorate, must not be null
098     * @param transformer  the transformer to use for conversion, must not be null
099     * @throws NullPointerException if set or transformer is null
100     */
101    protected TransformedSet(final Set<E> set, final Transformer<? super E, ? extends E> transformer) {
102        super(set, transformer);
103    }
104
105    @Override
106    public boolean equals(final Object object) {
107        return object == this || decorated().equals(object);
108    }
109
110    @Override
111    public int hashCode() {
112        return decorated().hashCode();
113    }
114
115}