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.BinaryFunction;
020import org.apache.commons.functor.BinaryPredicate;
021import org.apache.commons.lang3.Validate;
022
023/**
024 * Adapts a <code>Boolean</code>-valued {@link BinaryFunction BinaryFunction} to
025 * the {@link BinaryPredicate BinaryPredicate} interface.
026 * @param <L> the left argument type.
027 * @param <R> the right argument type.
028 * @version $Revision: 1537906 $ $Date: 2013-11-01 12:47:33 +0100 (Fr, 01 Nov 2013) $
029 */
030public final class BinaryFunctionBinaryPredicate<L, R> implements BinaryPredicate<L, R> {
031    /** The {@link BinaryFunction BinaryFunction} I'm wrapping. */
032    private final BinaryFunction<? super L, ? super R, Boolean> function;
033
034    /**
035     * Create an {@link BinaryPredicate BinaryPredicate} wrapping the given
036     * {@link BinaryFunction BinaryFunction}.
037     * @param function the {@link BinaryFunction BinaryFunction} to wrap
038     */
039    public BinaryFunctionBinaryPredicate(final BinaryFunction<? super L, ? super R, Boolean> function) {
040        this.function = Validate.notNull(function, "BinaryFunction argument must not be null");
041    }
042
043    /**
044     * {@inheritDoc} Returns the <code>boolean</code> value of the
045     * non-<code>null</code> <code>Boolean</code> returned by the
046     * {@link BinaryFunction#evaluate evaluate} method of my underlying
047     * function.
048     *
049     * The mehod throws NullPointerException if the underlying function returns
050     * <code>null</code>, and
051     * ClassCastException if the underlying function returns a
052     * non-<code>Boolean</code>
053     */
054    public boolean test(final L left, final R right) {
055        return function.evaluate(left, right).booleanValue();
056    }
057
058    /**
059     * {@inheritDoc}
060     */
061    @Override
062    public boolean equals(Object obj) {
063        if (obj == this) {
064            return true;
065        }
066        if (!(obj instanceof BinaryFunctionBinaryPredicate<?, ?>)) {
067            return false;
068        }
069        BinaryFunctionBinaryPredicate<?, ?> that = (BinaryFunctionBinaryPredicate<?, ?>) obj;
070        return this.function.equals(that.function);
071    }
072
073    /**
074     * {@inheritDoc}
075     */
076    @Override
077    public int hashCode() {
078        int hash = "BinaryFunctionBinaryPredicate".hashCode();
079        hash ^= function.hashCode();
080        return hash;
081    }
082
083    /**
084     * {@inheritDoc}
085     */
086    @Override
087    public String toString() {
088        return "BinaryFunctionBinaryPredicate<" + function + ">";
089    }
090
091    /**
092     * Adapt the given, possibly-<code>null</code>, {@link BinaryFunction
093     * BinaryFunction} to the {@link BinaryPredicate BinaryPredicate} interface.
094     * When the given <code>BinaryFunction</code> is <code>null</code>, returns
095     * <code>null</code>.
096     *
097     * @param <L> left type
098     * @param <R> right type
099     * @param <T> result type
100     * @param function the possibly-<code>null</code> {@link BinaryFunction
101     * BinaryFunction} to adapt
102     * @return a <code>BinaryFunctionBinaryPredicate</code> wrapping the given
103     * {@link BinaryFunction BinaryFunction}, or <code>null</code> if the given
104     * <code>BinaryFunction</code> is <code>null</code>
105     */
106    public static <L, R, T> BinaryFunctionBinaryPredicate<L, R> adapt(
107            final BinaryFunction<? super L, ? super R, Boolean> function) {
108        return null == function ? null : new BinaryFunctionBinaryPredicate<L, R>(function);
109    }
110
111}