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.functor.core.algorithm;
018
019import java.io.Serializable;
020import java.util.Iterator;
021
022import org.apache.commons.functor.BinaryProcedure;
023import org.apache.commons.functor.UnaryPredicate;
024import org.apache.commons.functor.core.composite.UnaryNot;
025
026/**
027 * Retain elements in left Iterator that match right UnaryPredicate.
028 *
029 * @param <T> the procedure argument type
030 * @version $Revision: 1344796 $ $Date: 2012-05-31 12:12:39 -0400 (Thu, 31 May 2012) $
031 */
032public final class RetainMatching<T>
033    implements BinaryProcedure<Iterator<? extends T>, UnaryPredicate<? super T>>, Serializable {
034    /**
035     * serialVersionUID declaration.
036     */
037    private static final long serialVersionUID = 6760018011875465469L;
038    /**
039     * A static {@code RetainMatching} instance reference.
040     */
041    private static final RetainMatching<Object> INSTANCE = new RetainMatching<Object>();
042    /**
043     * The {@code RemoveMatching} instance used to remove elements from input iterator.
044     */
045    private final RemoveMatching<T> removeMatching = new RemoveMatching<T>();
046
047    /**
048     * {@inheritDoc}
049     * @param left {@link Iterator}
050     * @param right {@link UnaryPredicate}
051     */
052    public void run(Iterator<? extends T> left, UnaryPredicate<? super T> right) {
053        removeMatching.run(left, UnaryNot.not(right));
054    }
055
056    /**
057     * {@inheritDoc}
058     */
059    @Override
060    public boolean equals(Object obj) {
061        return obj == this || obj != null && obj.getClass().equals(getClass());
062    }
063
064    /**
065     * {@inheritDoc}
066     */
067    @Override
068    public int hashCode() {
069        return System.identityHashCode(INSTANCE);
070    }
071
072    /**
073     * {@inheritDoc}
074     */
075    @Override
076    public String toString() {
077        return "RetainMatching";
078    }
079
080    /**
081     * Get a static {@link RetainMatching} instance.
082     * @return {@link RetainMatching}
083     */
084    public static RetainMatching<Object> instance() {
085        return INSTANCE;
086    }
087}