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.NullaryPredicate;
021import org.apache.commons.lang3.Validate;
022
023/**
024 * Adapts a <code>Boolean</code>-valued
025 * {@link NullaryFunction NullaryFunction} to the
026 * {@link NullaryPredicate NullaryPredicate} interface.
027 *
028 * @version $Revision: 1365377 $ $Date: 2012-07-24 21:59:23 -0300 (Tue, 24 Jul 2012) $
029 */
030public final class NullaryFunctionNullaryPredicate implements NullaryPredicate {
031
032    /** The {@link NullaryFunction NullaryFunction} I'm wrapping. */
033    private final NullaryFunction<Boolean> function;
034
035    /**
036     * Create a new NullaryFunctionNullaryPredicate.
037     * @param function to adapt
038     */
039    public NullaryFunctionNullaryPredicate(NullaryFunction<Boolean> function) {
040        this.function = Validate.notNull(function, "NullaryFunction argument was null");
041    }
042
043    /**
044     * Returns the <code>boolean</code> value of the non-<code>null</code>
045     * <code>Boolean</code> returned by the {@link NullaryFunction#evaluate evaluate}
046     * method of my underlying function.
047     * {@inheritDoc}
048     */
049    public boolean test() {
050        return function.evaluate().booleanValue();
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 NullaryFunctionNullaryPredicate)) {
062            return false;
063        }
064        NullaryFunctionNullaryPredicate that = (NullaryFunctionNullaryPredicate) obj;
065        return this.function.equals(that.function);
066    }
067
068    /**
069     * {@inheritDoc}
070     */
071    @Override
072    public int hashCode() {
073        int hash = "NullaryFunctionNullaryPredicate".hashCode();
074        hash ^= function.hashCode();
075        return hash;
076    }
077
078    /**
079     * {@inheritDoc}
080     */
081    @Override
082    public String toString() {
083        return "NullaryFunctionNullaryPredicate<" + function + ">";
084    }
085
086    /**
087     * Adapt a NullaryFunction as a NullaryPredicate.
088     * @param function to adapt
089     * @return NullaryFunctionNullaryPredicate
090     */
091    public static NullaryFunctionNullaryPredicate adapt(NullaryFunction<Boolean> function) {
092        return null == function ? null : new NullaryFunctionNullaryPredicate(function);
093    }
094}