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 java.io.Serializable;
020
021import org.apache.commons.functor.Function;
022import org.apache.commons.functor.Procedure;
023import org.apache.commons.lang3.Validate;
024
025/**
026 * Adapts a
027 * {@link Procedure Procedure}
028 * to the
029 * {@link Function Function} interface
030 * by always returning <code>null</code>.
031 * <p/>
032 * Note that although this class implements
033 * {@link Serializable}, a given instance will
034 * only be truly <code>Serializable</code> if the
035 * underlying procedure is.  Attempts to serialize
036 * an instance whose delegate is not
037 * <code>Serializable</code> will result in an exception.
038 *
039 * @param <T> the returned value type.
040 * @version $Revision: 1365377 $ $Date: 2012-07-24 20:59:23 -0400 (Tue, 24 Jul 2012) $
041 */
042public final class ProcedureFunction<T> implements Function<T>, Serializable {
043    /**
044     * serialVersionUID declaration.
045     */
046    private static final long serialVersionUID = -655207616317672341L;
047    /** The {@link Procedure Procedure} I'm wrapping. */
048    private final Procedure procedure;
049
050    /**
051     * Create a new ProcedureFunction.
052     * @param procedure to adapt
053     */
054    public ProcedureFunction(Procedure procedure) {
055        this.procedure = Validate.notNull(procedure, "Procedure argument was null");
056    }
057
058    /**
059     * {@inheritDoc}
060     */
061    public T evaluate() {
062        procedure.run();
063        return null;
064    }
065
066    /**
067     * {@inheritDoc}
068     */
069    @Override
070    public boolean equals(Object that) {
071        return that == this || (that instanceof ProcedureFunction<?> && equals((ProcedureFunction<?>) that));
072    }
073
074    /**
075     * Learn whether another ProcedureFunction is equal to this.
076     * @param that ProcedureFunction to test
077     * @return boolean
078     */
079    public boolean equals(ProcedureFunction<?> that) {
080        return null != that && procedure.equals(that.procedure);
081    }
082
083    /**
084     * {@inheritDoc}
085     */
086    @Override
087    public int hashCode() {
088        int hash = "ProcedureFunction".hashCode();
089        hash ^= procedure.hashCode();
090        return hash;
091    }
092
093    /**
094     * {@inheritDoc}
095     */
096    @Override
097    public String toString() {
098        return "ProcedureFunction<" + procedure + ">";
099    }
100
101    /**
102     * Adapt a Procedure as a Function.
103     * @param <T> the returned value type.
104     * @param procedure to adapt
105     * @return ProcedureFunction<T>
106     */
107    public static <T> ProcedureFunction<T> adapt(Procedure procedure) {
108        return null == procedure ? null : new ProcedureFunction<T>(procedure);
109    }
110
111}