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.collection;
018
019 import java.io.Serializable;
020 import java.lang.reflect.Array;
021 import java.util.Collection;
022 import java.util.Map;
023
024 import org.apache.commons.functor.UnaryPredicate;
025
026 /**
027 * @version $Revision: 1166333 $ $Date: 2011-09-07 21:36:42 +0200 (Wed, 07 Sep 2011) $
028 * @author Rodney Waldhoff
029 */
030 public final class IsEmpty<A> implements UnaryPredicate<A>, Serializable {
031
032 // class variables
033 // ------------------------------------------------------------------------
034
035 /**
036 * Basic IsEmpty instance.
037 */
038 public static final IsEmpty<Object> INSTANCE = new IsEmpty<Object>();
039
040 /**
041 * serialVersionUID declaration.
042 */
043 private static final long serialVersionUID = 6555097970639642373L;
044
045 // constructor
046 // ------------------------------------------------------------------------
047 /**
048 * Create a new IsEmpty.
049 */
050 public IsEmpty() {
051 }
052
053 // instance methods
054 // ------------------------------------------------------------------------
055 /**
056 * {@inheritDoc}
057 */
058 public boolean test(A obj) {
059 if (obj instanceof Collection<?>) {
060 return testCollection((Collection<?>) obj);
061 }
062 if (obj instanceof Map<?, ?>) {
063 return testMap((Map<?, ?>) obj);
064 }
065 if (obj instanceof String) {
066 return testString((String) obj);
067 }
068 if (null != obj && obj.getClass().isArray()) {
069 return testArray(obj);
070 }
071 if (null == obj) {
072 throw new IllegalArgumentException("Argument must not be null");
073 }
074 throw new IllegalArgumentException("Expected Collection, Map, String or Array, found " + obj.getClass());
075 }
076
077 /**
078 * {@inheritDoc}
079 */
080 public boolean equals(Object that) {
081 return that instanceof IsEmpty<?>;
082 }
083
084 /**
085 * {@inheritDoc}
086 */
087 public int hashCode() {
088 return "IsEmpty".hashCode();
089 }
090
091 /**
092 * {@inheritDoc}
093 */
094 public String toString() {
095 return "IsEmpty()";
096 }
097
098 /**
099 * Test a collection.
100 * @param col to test
101 * @return boolean
102 */
103 private boolean testCollection(Collection<?> col) {
104 return col.isEmpty();
105 }
106
107 /**
108 * Test a map.
109 * @param map to test
110 * @return boolean
111 */
112 private boolean testMap(Map<?, ?> map) {
113 return map.isEmpty();
114 }
115
116 /**
117 * Test a string.
118 * @param str to test
119 * @return boolean
120 */
121 private boolean testString(String str) {
122 return 0 == str.length();
123 }
124
125 /**
126 * Test an array.
127 * @param array to test
128 * @return boolean
129 */
130 private boolean testArray(Object array) {
131 return 0 == Array.getLength(array);
132 }
133
134 // static
135 // ------------------------------------------------------------------------
136 /**
137 * Get an IsEmpty instance.
138 * @return IsEmpty
139 */
140 public static <A> IsEmpty<A> instance() {
141 return new IsEmpty<A>();
142 }
143
144 }