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.BinaryFunction;
022import org.apache.commons.functor.UnaryFunction;
023import org.apache.commons.lang3.Validate;
024
025/**
026 * Adapts a
027 * {@link UnaryFunction UnaryFunction}
028 * to the
029 * {@link BinaryFunction BinaryFunction} interface
030 * by ignoring the first binary argument.
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 functor is.  Attempts to serialize
036 * an instance whose delegate is not
037 * <code>Serializable</code> will result in an exception.
038 *
039 * @param <L> the left argument type.
040 * @param <R> the right argument type.
041 * @param <T> the returned value type.
042 * @version $Revision: 1365377 $ $Date: 2012-07-24 20:59:23 -0400 (Tue, 24 Jul 2012) $
043 */
044public final class IgnoreLeftFunction<L, R, T> implements BinaryFunction<L, R, T>, Serializable {
045    /**
046     * serialVersionUID declaration.
047     */
048    private static final long serialVersionUID = 4677703245851183542L;
049    /** The {@link UnaryFunction UnaryFunction} I'm wrapping. */
050    private final UnaryFunction<? super R, ? extends T> function;
051
052    /**
053     * Create a new IgnoreLeftFunction.
054     * @param function UnaryFunction for right argument
055     */
056    public IgnoreLeftFunction(UnaryFunction<? super R, ? extends T> function) {
057        this.function = Validate.notNull(function, "UnaryFunction argument was null");
058    }
059
060    /**
061     * {@inheritDoc}
062     */
063    public T evaluate(L left, R right) {
064        return function.evaluate(right);
065    }
066
067    /**
068     * {@inheritDoc}
069     */
070    @Override
071    public boolean equals(Object that) {
072        return that == this || (that instanceof IgnoreLeftFunction<?, ?, ?>
073                && equals((IgnoreLeftFunction<?, ?, ?>) that));
074    }
075
076    /**
077     * Learn whether another IgnoreLeftFunction is equal to this.
078     * @param that IgnoreLeftFunction to test
079     * @return boolean
080     */
081    public boolean equals(IgnoreLeftFunction<?, ?, ?> that) {
082        return null != that && function.equals(that.function);
083    }
084
085    /**
086     * {@inheritDoc}
087     */
088    @Override
089    public int hashCode() {
090        int hash = "IgnoreLeftFunction".hashCode();
091        hash ^= function.hashCode();
092        return hash;
093    }
094
095    /**
096     * {@inheritDoc}
097     */
098    @Override
099    public String toString() {
100        return "IgnoreLeftFunction<" + function + ">";
101    }
102
103    /**
104     * Adapt a UnaryFunction to the BinaryFunction interface.
105     * @param <L> left type
106     * @param <R> right type
107     * @param <T> result type
108     * @param function to adapt
109     * @return IgnoreLeftFunction
110     */
111    public static <L, R, T> IgnoreLeftFunction<L, R, T> adapt(UnaryFunction<? super R, ? extends T> function) {
112        return null == function ? null : new IgnoreLeftFunction<L, R, T>(function);
113    }
114
115}