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.NullaryFunction;
020import org.apache.commons.functor.NullaryProcedure;
021import org.apache.commons.lang3.Validate;
022
023/**
024 * Adapts a
025 * {@link NullaryProcedure NullaryProcedure}
026 * to the
027 * {@link NullaryFunction NullaryFunction} interface
028 * by always returning <code>null</code>.
029 *
030 * @param <T> the returned value type.
031 * @version $Revision: 1365377 $ $Date: 2012-07-24 21:59:23 -0300 (Tue, 24 Jul 2012) $
032 */
033public final class NullaryProcedureNullaryFunction<T> implements NullaryFunction<T> {
034    /** The {@link NullaryProcedure NullaryProcedure} I'm wrapping. */
035    private final NullaryProcedure procedure;
036
037    /**
038     * Create a new NullaryProcedureNullaryFunction.
039     * @param procedure to adapt
040     */
041    public NullaryProcedureNullaryFunction(NullaryProcedure procedure) {
042        this.procedure = Validate.notNull(procedure, "NullaryProcedure argument was null");
043    }
044
045    /**
046     * {@inheritDoc}
047     */
048    public T evaluate() {
049        procedure.run();
050        return null;
051    }
052
053    /**
054     * {@inheritDoc}
055     */
056    @Override
057    public boolean equals(Object obj) {
058        if (obj == this) {
059            return true;
060        }
061        if (!(obj instanceof NullaryProcedureNullaryFunction<?>)) {
062            return false;
063        }
064        NullaryProcedureNullaryFunction<?> that = (NullaryProcedureNullaryFunction<?>) obj;
065        return this.procedure.equals(that.procedure);
066    }
067
068    /**
069     * {@inheritDoc}
070     */
071    @Override
072    public int hashCode() {
073        int hash = "NullaryProcedureNullaryFunction".hashCode();
074        hash ^= procedure.hashCode();
075        return hash;
076    }
077
078    /**
079     * {@inheritDoc}
080     */
081    @Override
082    public String toString() {
083        return "NullaryProcedureNullaryFunction<" + procedure + ">";
084    }
085
086    /**
087     * Adapt a NullaryProcedure as a NullaryFunction.
088     * @param <T> the returned value type.
089     * @param procedure to adapt
090     * @return NullaryProcedureNullaryFunction<T>
091     */
092    public static <T> NullaryProcedureNullaryFunction<T> adapt(NullaryProcedure procedure) {
093        return null == procedure ? null : new NullaryProcedureNullaryFunction<T>(procedure);
094    }
095
096}