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.adapter;
018
019import org.apache.commons.functor.Function;
020import org.apache.commons.functor.Procedure;
021import org.apache.commons.lang3.Validate;
022
023/**
024 * Adapts a
025 * {@link Procedure Procedure}
026 * to the
027 * {@link Function Function} interface
028 * by always returning <code>null</code>.
029 *
030 * @param <A> the argument type.
031 * @param <T> the returned value type.
032 * @version $Revision: 1537906 $ $Date: 2013-11-01 12:47:33 +0100 (Fr, 01 Nov 2013) $
033 */
034public final class ProcedureFunction<A, T> implements Function<A, T> {
035    /** The {@link Procedure Procedure} I'm wrapping. */
036    private final Procedure<? super A> procedure;
037
038    /**
039     * Create a new ProcedureFunction.
040     * @param procedure to adapt
041     */
042    public ProcedureFunction(Procedure<? super A> procedure) {
043        this.procedure = Validate.notNull(procedure, "Procedure argument was null");
044    }
045
046    /**
047     * {@inheritDoc}
048     */
049    public T evaluate(A obj) {
050        procedure.run(obj);
051        return null;
052    }
053
054    /**
055     * {@inheritDoc}
056     */
057    @Override
058    public boolean equals(Object obj) {
059        if (obj == this) {
060            return true;
061        }
062        if (!(obj instanceof ProcedureFunction<?, ?>)) {
063            return false;
064        }
065        ProcedureFunction<?, ?> that = (ProcedureFunction<?, ?>) obj;
066        return this.procedure.equals(that.procedure);
067    }
068
069    /**
070     * {@inheritDoc}
071     */
072    @Override
073    public int hashCode() {
074        int hash = "ProcedureFunction".hashCode();
075        hash ^= procedure.hashCode();
076        return hash;
077    }
078
079    /**
080     * {@inheritDoc}
081     */
082    @Override
083    public String toString() {
084        return "ProcedureFunction<" + procedure + ">";
085    }
086
087    /**
088     * Adapt a Procedure to the Function interface.
089     * @param <A> the argument type.
090     * @param <T> the returned value type.
091     * @param procedure to adapt
092     * @return ProcedureFunction
093     */
094    public static <A, T> ProcedureFunction<A, T> adapt(Procedure<? super A> procedure) {
095        return null == procedure ? null : new ProcedureFunction<A, T>(procedure);
096    }
097
098}