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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.collections4.functors;
18  
19  import java.io.Serializable;
20  
21  import org.apache.commons.collections4.Closure;
22  import org.apache.commons.collections4.Transformer;
23  
24  /**
25   * Transformer implementation that calls a Closure using the input object
26   * and then returns the input.
27   *
28   * @since 3.0
29   */
30  public class ClosureTransformer<T> implements Transformer<T, T>, Serializable {
31  
32      /** Serial version UID */
33      private static final long serialVersionUID = 478466901448617286L;
34  
35      /** The closure to wrap */
36      private final Closure<? super T> iClosure;
37  
38      /**
39       * Factory method that performs validation.
40       *
41       * @param <T>  the type of the object to transform
42       * @param closure  the closure to call, not null
43       * @return the <code>closure</code> transformer
44       * @throws NullPointerException if the closure is null
45       */
46      public static <T> Transformer<T, T> closureTransformer(final Closure<? super T> closure) {
47          if (closure == null) {
48              throw new NullPointerException("Closure must not be null");
49          }
50          return new ClosureTransformer<>(closure);
51      }
52  
53      /**
54       * Constructor that performs no validation.
55       * Use <code>closureTransformer</code> if you want that.
56       *
57       * @param closure  the closure to call, not null
58       */
59      public ClosureTransformer(final Closure<? super T> closure) {
60          super();
61          iClosure = closure;
62      }
63  
64      /**
65       * Transforms the input to result by executing a closure.
66       *
67       * @param input  the input object to transform
68       * @return the transformed result
69       */
70      @Override
71      public T transform(final T input) {
72          iClosure.execute(input);
73          return input;
74      }
75  
76      /**
77       * Gets the closure.
78       *
79       * @return the closure
80       * @since 3.1
81       */
82      public Closure<? super T> getClosure() {
83          return iClosure;
84      }
85  
86  }