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.Function;
021import org.apache.commons.lang3.Validate;
022
023/**
024 * Adapts a
025 * {@link NullaryFunction NullaryFunction}
026 * to the
027 * {@link Function Function} interface
028 * by ignoring the unary argument.
029 *
030 * @param <A> the argument type.
031 * @param <T> the returned value type.
032 * @version $Revision: 1365377 $ $Date: 2012-07-24 21:59:23 -0300 (Tue, 24 Jul 2012) $
033 */
034public final class NullaryFunctionFunction<A, T> implements Function<A, T> {
035    /** The {@link NullaryFunction NullaryFunction} I'm wrapping. */
036    private final NullaryFunction<? extends T> function;
037
038    /**
039     * Create a new NullaryFunctionFunction.
040     * @param function to adapt
041     */
042    public NullaryFunctionFunction(NullaryFunction<? extends T> function) {
043        this.function = Validate.notNull(function, "NullaryFunction argument was null");
044    }
045
046    /**
047     * {@inheritDoc}
048     */
049    public T evaluate(A obj) {
050        return function.evaluate();
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 NullaryFunctionFunction<?, ?>)) {
062            return false;
063        }
064        NullaryFunctionFunction<?, ?> that = (NullaryFunctionFunction<?, ?>) obj;
065        return this.function.equals(that.function);
066    }
067
068    /**
069     * {@inheritDoc}
070     */
071    @Override
072    public int hashCode() {
073        int hash = "NullaryFunctionFunction".hashCode();
074        hash ^= function.hashCode();
075        return hash;
076    }
077
078    /**
079     * {@inheritDoc}
080     */
081    @Override
082    public String toString() {
083        return "NullaryFunctionFunction<" + function + ">";
084    }
085
086    /**
087     * Adapt a NullaryFunction to the Function interface.
088     * @param <A> arg type
089     * @param <T> result type
090     * @param function to adapt
091     * @return NullaryFunctionFunction
092     */
093    public static <A, T> NullaryFunctionFunction<A, T> adapt(NullaryFunction<? extends T> function) {
094        return null == function ? null : new NullaryFunctionFunction<A, T>(function);
095    }
096
097}