    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</code> 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 * This class is Serializable from Commons Collections 3.1.
    033 *
    034 * @param <E> the type of the elements in this set
    035 * @since 3.0
    036 */
    037public class TransformedSet<E> extends TransformedCollection<E> implements Set<E> {
    038
    039    /** Serialization version */
    040    private static final long serialVersionUID = 306127383500410386L;
    041
    042    /**
    043     * Factory method to create a transforming set.
    044     * <p>
    045     * If there are any elements already in the set being decorated, they
    046     * are NOT transformed.
    047     * Contrast this with {@link #transformedSet(Set, Transformer)}.
    048     *
    049     * @param <E> the element type
    050     * @param set  the set to decorate, must not be null
    051     * @param transformer  the transformer to use for conversion, must not be null
    052     * @return a new transformed set
    053     * @throws NullPointerException if set or transformer is null
    054     * @since 4.0
    055     */
    056    public static <E> TransformedSet<E> transformingSet(final Set<E> set,
    057            final Transformer<? super E, ? extends E> transformer) {
    058        return new TransformedSet<>(set, transformer);
    059    }
    060
    061    /**
    062     * Factory method to create a transforming set that will transform
    063     * existing contents of the specified set.
    064     * <p>
    065     * If there are any elements already in the set being decorated, they
    066     * will be transformed by this method.
    067     * Contrast this with {@link #transformingSet(Set, Transformer)}.
    068     *
    069     * @param <E> the element type
    070     * @param set  the set to decorate, must not be null
    071     * @param transformer  the transformer to use for conversion, must not be null
    072     * @return a new transformed set
    073     * @throws NullPointerException if set or transformer is null
    074     * @since 4.0
    075     */
    076    public static <E> Set<E> transformedSet(final Set<E> set, final Transformer<? super E, ? extends E> transformer) {
    077        final TransformedSet<E> decorated = new TransformedSet<>(set, transformer);
    078        if (set.size() > 0) {
    079            @SuppressWarnings("unchecked") // set is type E
    080            final E[] values = (E[]) set.toArray(); // NOPMD - false positive for generics
    081            set.clear();
    082            for (final E value : values) {
    083                decorated.decorated().add(transformer.transform(value));
    084            }
    085        }
    086        return decorated;
    087    }
    088
    089    //-----------------------------------------------------------------------
    090    /**
    091     * Constructor that wraps (not copies).
    092     * <p>
    093     * If there are any elements already in the set being decorated, they
    094     * are NOT transformed.
    095     *
    096     * @param set  the set to decorate, must not be null
    097     * @param transformer  the transformer to use for conversion, must not be null
    098     * @throws NullPointerException if set or transformer is null
    099     */
    100    protected TransformedSet(final Set<E> set, final Transformer<? super E, ? extends E> transformer) {
    101        super(set, transformer);
    102    }
    103
    104    @Override
    105    public boolean equals(final Object object) {
    106        return object == this || decorated().equals(object);
    107    }
    108
    109    @Override
    110    public int hashCode() {
    111        return decorated().hashCode();
    112    }
    113
    114}