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1   ////////////////////////////////////////////////////////////////////////////////
2   // checkstyle: Checks Java source code for adherence to a set of rules.
3   // Copyright (C) 2001-2017 the original author or authors.
4   //
5   // This library is free software; you can redistribute it and/or
6   // modify it under the terms of the GNU Lesser General Public
7   // License as published by the Free Software Foundation; either
8   // version 2.1 of the License, or (at your option) any later version.
9   //
10  // This library is distributed in the hope that it will be useful,
11  // but WITHOUT ANY WARRANTY; without even the implied warranty of
12  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13  // Lesser General Public License for more details.
14  //
15  // You should have received a copy of the GNU Lesser General Public
16  // License along with this library; if not, write to the Free Software
17  // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
18  ////////////////////////////////////////////////////////////////////////////////
19  
20  package com.puppycrawl.tools.checkstyle;
21  
22  import java.util.Enumeration;
23  import java.util.HashMap;
24  import java.util.Map;
25  import java.util.Properties;
26  
27  /**
28   * Resolves external properties from an
29   * underlying {@code Properties} object.
30   *
31   * @author lkuehne
32   */
33  public final class PropertiesExpander
34      implements PropertyResolver {
35      /** The underlying values. */
36      private final Map<String, String> values;
37  
38      /**
39       * Creates a new PropertiesExpander.
40       * @param properties the underlying properties to use for
41       *     property resolution.
42       * @throws IllegalArgumentException indicates null was passed
43       */
44      public PropertiesExpander(Properties properties) {
45          if (properties == null) {
46              throw new IllegalArgumentException("cannot pass null");
47          }
48          values = new HashMap<>(properties.size());
49          for (Enumeration<?> e = properties.propertyNames(); e.hasMoreElements();) {
50              final String name = (String) e.nextElement();
51              values.put(name, properties.getProperty(name));
52          }
53      }
54  
55      @Override
56      public String resolve(String name) {
57          return values.get(name);
58      }
59  }