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 java.io.Serializable;
020
021 import org.apache.commons.functor.BinaryPredicate;
022 import org.apache.commons.functor.UnaryPredicate;
023 import org.apache.commons.functor.adapter.RightBoundPredicate;
024
025 /**
026 * {@link #test Tests}
027 * <code>true</code> iff its argument
028 * {@link Class#isInstance is an instance}
029 * of some specified {@link Class Class}.
030 *
031 * @param <T> the object instance has to be tested against the input class.
032 * @version $Revision: 1160394 $ $Date: 2011-08-22 21:40:35 +0200 (Mon, 22 Aug 2011) $
033 * @author Rodney Waldhoff
034 */
035 public final class IsInstance<T> implements BinaryPredicate<T, Class<?>>, Serializable {
036 /**
037 * Basic IsInstanceOf instance.
038 */
039 public static final IsInstance<Object> INSTANCE = IsInstance.<Object>instance();
040 /**
041 * serialVersionUID declaration.
042 */
043 private static final long serialVersionUID = 9104265415387129627L;
044 /**
045 * The non zero number used to shift the initial hashcode.
046 */
047 private static final int NONZERO_SHIFT_NUMBER = 4;
048 /**
049 * The non zero number used to bitwise or the hashcode.
050 */
051 private static final int NONZERO_BITWISE_NUMBER = 37;
052
053 // predicate interface
054 // ------------------------------------------------------------------------
055
056 /**
057 * {@inheritDoc}
058 */
059 public boolean test(T left, Class<?> right) {
060 return right.isInstance(left);
061 }
062
063 /**
064 * {@inheritDoc}
065 */
066 public boolean equals(Object that) {
067 return that instanceof IsInstance<?>;
068 }
069
070 /**
071 * {@inheritDoc}
072 */
073 public int hashCode() {
074 return ("IsInstance".hashCode() << NONZERO_SHIFT_NUMBER) | NONZERO_BITWISE_NUMBER;
075 }
076
077 /**
078 * {@inheritDoc}
079 */
080 public String toString() {
081 return "IsInstance";
082 }
083
084 /**
085 * Get an IsInstance instance.
086 * @param <T> the object instance has to be tested against the input class.
087 * @return IsInstance<T>
088 */
089 public static <T> IsInstance<T> instance() {
090 return new IsInstance<T>();
091 }
092
093 /**
094 * Get an IsInstanceOf UnaryPredicate.
095 * @param <T> the object instance has to be tested against the input class.
096 * @param clazz bound right-side argument
097 * @return UnaryPredicate<T>
098 */
099 public static <T> UnaryPredicate<T> of(Class<?> clazz) {
100 return RightBoundPredicate.bind(new IsInstance<T>(), clazz);
101 }
102 }