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 */
017 package org.apache.commons.functor.core;
018
019 import org.apache.commons.functor.BinaryFunction;
020 import org.apache.commons.functor.BinaryPredicate;
021 import org.apache.commons.functor.adapter.BinaryFunctionBinaryPredicate;
022 import org.apache.commons.functor.adapter.IgnoreLeftFunction;
023
024 /**
025 * Holder class for a right-identity <code>BinaryFunction</code> (evaluates to the right argument) and a right-identity
026 * <code>BinaryPredicate</code> (tests whether right <code>Boolean</code> argument equals <code>Boolean.TRUE</code>).
027 *
028 * @version $Revision: 1160415 $ $Date: 2011-08-22 22:14:38 +0200 (Mon, 22 Aug 2011) $
029 * @author Rodney Waldhoff
030 * @author Matt Benson
031 */
032 public final class RightIdentity {
033
034 // static attributes
035 // ------------------------------------------------------------------------
036 /**
037 * Right-identity function.
038 */
039 public static final BinaryFunction<Object, Object, Object> FUNCTION = RightIdentity.<Object, Object>function();
040
041 /**
042 * Right-identity predicate.
043 */
044 public static final BinaryPredicate<Object, Boolean> PREDICATE =
045 BinaryFunctionBinaryPredicate.adapt(IgnoreLeftFunction.adapt(new Identity<Boolean>()));
046
047 // constructor
048 // ------------------------------------------------------------------------
049 /**
050 * Create a new RightIdentity.
051 */
052 public RightIdentity() {
053 }
054
055 // static methods
056 // ------------------------------------------------------------------------
057
058 /**
059 * Get a typed right-identity BinaryFunction.
060 * @param <L> the left argument type.
061 * @param <R> the right argument type.
062 * @return BinaryFunction<L, R, R>
063 */
064 public static <L, R> BinaryFunction<L, R, R> function() {
065 return IgnoreLeftFunction.adapt(new Identity<R>());
066 }
067
068 /**
069 * Get a typed right-identity BinaryPredicate.
070 * @param <L> the left argument type.
071 * @return BinaryPredicate<L, Boolean>
072 */
073 public static <L> BinaryPredicate<L, Boolean> predicate() {
074 return BinaryFunctionBinaryPredicate.adapt(
075 IgnoreLeftFunction.<L, Boolean, Boolean>adapt(new Identity<Boolean>()));
076 }
077 }