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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  
18  package org.apache.commons.collections4.properties;
19  
20  import java.util.ArrayList;
21  import java.util.Collections;
22  import java.util.Enumeration;
23  import java.util.List;
24  import java.util.Properties;
25  import java.util.Set;
26  
27  import org.apache.commons.collections4.iterators.IteratorEnumeration;
28  
29  /**
30   * A drop-in replacement for {@link Properties} for sorting keys.
31   * <p>
32   * Overrides {@link Properties#keys()} to sort keys. Allows other methods on the superclass to work with sorted keys.
33   * </p>
34   *
35   * @since 4.2
36   */
37  public class SortedProperties extends Properties {
38  
39      private static final long serialVersionUID = 1L;
40  
41      @Override
42      public synchronized Enumeration<Object> keys() {
43          final Set<Object> keySet = keySet();
44          final List<String> keys = new ArrayList<>(keySet.size());
45          for (final Object key : keySet) {
46              keys.add(key.toString());
47          }
48          Collections.sort(keys);
49          return new IteratorEnumeration<>(keys.iterator());
50      }
51  }