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.adapter;
018
019 import java.io.Serializable;
020
021 import org.apache.commons.functor.Function;
022 import org.apache.commons.functor.UnaryFunction;
023
024 /**
025 * Adapts a
026 * {@link Function Function}
027 * to the
028 * {@link UnaryFunction UnaryFunction} interface
029 * by ignoring the unary argument.
030 * <p/>
031 * Note that although this class implements
032 * {@link Serializable}, a given instance will
033 * only be truly <code>Serializable</code> if the
034 * underlying functor is. Attempts to serialize
035 * an instance whose delegate is not
036 * <code>Serializable</code> will result in an exception.
037 *
038 * @param <A> the argument type.
039 * @param <T> the returned value type.
040 * @version $Revision: 1157609 $ $Date: 2011-08-14 21:42:21 +0200 (Sun, 14 Aug 2011) $
041 * @author Rodney Waldhoff
042 */
043 public final class FunctionUnaryFunction<A, T> implements UnaryFunction<A, T>, Serializable {
044 /**
045 * serialVersionUID declaration.
046 */
047 private static final long serialVersionUID = 1993899041200996524L;
048 /** The {@link Function Function} I'm wrapping. */
049 private final Function<? extends T> function;
050
051 /**
052 * Create a new FunctionUnaryFunction.
053 * @param function to adapt
054 */
055 public FunctionUnaryFunction(Function<? extends T> function) {
056 if (function == null) {
057 throw new IllegalArgumentException("Function argument was null");
058 }
059 this.function = function;
060 }
061
062 /**
063 * {@inheritDoc}
064 */
065 public T evaluate(A obj) {
066 return function.evaluate();
067 }
068
069 /**
070 * {@inheritDoc}
071 */
072 public boolean equals(Object that) {
073 return that == this || (that instanceof FunctionUnaryFunction<?, ?>
074 && equals((FunctionUnaryFunction<?, ?>) that));
075 }
076
077 /**
078 * Learn whether another FunctionUnaryFunction is equal to this.
079 * @param that FunctionUnaryFunction to test
080 * @return boolean
081 */
082 public boolean equals(FunctionUnaryFunction<?, ?> that) {
083 return null != that && (null == function ? null == that.function : function.equals(that.function));
084 }
085
086 /**
087 * {@inheritDoc}
088 */
089 public int hashCode() {
090 int hash = "FunctionUnaryFunction".hashCode();
091 if (null != function) {
092 hash ^= function.hashCode();
093 }
094 return hash;
095 }
096
097 /**
098 * {@inheritDoc}
099 */
100 public String toString() {
101 return "FunctionUnaryFunction<" + function + ">";
102 }
103
104 /**
105 * Adapt a Function to the UnaryFunction interface.
106 * @param <A> arg type
107 * @param <T> result type
108 * @param function to adapt
109 * @return FunctionUnaryFunction
110 */
111 public static <A, T> FunctionUnaryFunction<A, T> adapt(Function<? extends T> function) {
112 return null == function ? null : new FunctionUnaryFunction<A, T>(function);
113 }
114
115 }