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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.commons.functor.core.composite;
18  
19  import java.io.Serializable;
20  
21  import org.apache.commons.functor.BinaryPredicate;
22  import org.apache.commons.functor.BinaryProcedure;
23  import org.apache.commons.functor.core.NoOp;
24  
25  /**
26   * A {@link BinaryProcedure BinaryProcedure}
27   * similiar to Java's "ternary"
28   * or "conditional" operator (<code>&#x3F; &#x3A;</code>).
29   * Given a {@link BinaryPredicate predicate}
30   * <i>p</i> and {@link BinaryProcedure procedures}
31   * <i>q</i> and <i>r</i>, {@link #run runs}
32   * <code>if (p.test(x,y)) { q.run(x,y); } else { r.run(x,y); }</code>.
33   * <p>
34   * Note that although this class implements
35   * {@link Serializable}, a given instance will
36   * only be truly <code>Serializable</code> if all the
37   * underlying functors are.  Attempts to serialize
38   * an instance whose delegates are not all
39   * <code>Serializable</code> will result in an exception.
40   * </p>
41   * @version $Revision: 1166384 $ $Date: 2011-09-07 22:22:00 +0200 (Wed, 07 Sep 2011) $
42   * @author Rodney Waldhoff
43   */
44  public final class ConditionalBinaryProcedure<L, R> implements BinaryProcedure<L, R>, Serializable {
45  
46      /**
47       * serialVersionUID declaration.
48       */
49      private static final long serialVersionUID = -3521992036791188475L;
50  
51      /** Base hash integer used to shift hash */
52      private static final int HASH_SHIFT = 4;
53      // attributes
54      // ------------------------------------------------------------------------
55      private final BinaryPredicate<? super L, ? super R> ifPred;
56      private final BinaryProcedure<? super L, ? super R> thenProc;
57      private final BinaryProcedure<? super L, ? super R> elseProc;
58  
59      // constructor
60      // ------------------------------------------------------------------------
61  
62      /**
63       * Create a new ConditionalBinaryProcedure.
64       * @param ifPred to evaluate
65       * @param thenProc if <code>ifPred</code> yields <code>true</code>
66       */
67      public ConditionalBinaryProcedure(BinaryPredicate<? super L, ? super R> ifPred,
68              BinaryProcedure<? super L, ? super R> thenProc) {
69          this(ifPred, thenProc, NoOp.instance());
70      }
71  
72      /**
73       * Create a new ConditionalBinaryProcedure.
74       * @param ifPred to evaluate
75       * @param thenProc if <code>ifPred</code> yields <code>true</code>
76       * @param elseProc if <code>ifPred</code> yields <code>false</code>
77       */
78      public ConditionalBinaryProcedure(BinaryPredicate<? super L, ? super R> ifPred,
79              BinaryProcedure<? super L, ? super R> thenProc, BinaryProcedure<? super L, ? super R> elseProc) {
80          if (ifPred == null) {
81              throw new IllegalArgumentException("BinaryPredicate argument was null");
82          }
83          this.ifPred = ifPred;
84          if (thenProc == null || elseProc == null) {
85              throw new IllegalArgumentException("One or more BinaryProcedure arguments was null");
86          }
87          this.thenProc = thenProc;
88          this.elseProc = elseProc;
89      }
90  
91      // predicate interface
92      // ------------------------------------------------------------------------
93  
94      /**
95       * {@inheritDoc}
96       */
97      public void run(L left, R right) {
98          if (ifPred.test(left, right)) {
99              thenProc.run(left, right);
100         } else {
101             elseProc.run(left, right);
102         }
103     }
104 
105     /**
106      * {@inheritDoc}
107      */
108     public boolean equals(Object that) {
109         return that == this || (that instanceof ConditionalBinaryProcedure<?, ?>
110                                     && equals((ConditionalBinaryProcedure<?, ?>) that));
111     }
112 
113     /**
114      * Learn whether a given ConditionalBinaryProcedure is equal to this.
115      * @param that compared object
116      * @return boolean
117      */
118     public boolean equals(ConditionalBinaryProcedure<?, ?> that) {
119         return null != that
120                 && (null == ifPred ? null == that.ifPred : ifPred.equals(that.ifPred))
121                 && (null == thenProc ? null == that.thenProc : thenProc.equals(that.thenProc))
122                 && (null == elseProc ? null == that.elseProc : elseProc.equals(that.elseProc));
123     }
124 
125     /**
126      * {@inheritDoc}
127      */
128     public int hashCode() {
129         int hash = "ConditionalBinaryProcedure".hashCode();
130         if (null != ifPred) {
131             hash <<= HASH_SHIFT;
132             hash ^= ifPred.hashCode();
133         }
134         if (null != thenProc) {
135             hash <<= HASH_SHIFT;
136             hash ^= thenProc.hashCode();
137         }
138         if (null != elseProc) {
139             hash <<= HASH_SHIFT;
140             hash ^= elseProc.hashCode();
141         }
142         return hash;
143     }
144 
145     /**
146      * {@inheritDoc}
147      */
148     public String toString() {
149         return "ConditionalBinaryProcedure<" + ifPred + "?" + thenProc + ":" + elseProc + ">";
150     }
151 }