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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.logging.log4j.core.util;
18  
19  import java.util.HashSet;
20  import java.util.Set;
21  
22  /**
23   * Set-related convenience methods.
24   */
25  public final class SetUtils {
26      private SetUtils() {
27      }
28  
29      /**
30       * Extracts the Strings from a Set that start with a given prefix.
31       *
32       * @param set a Set of Strings (assumed to all be non-{@code null})
33       * @param prefix the prefix to look for in the string set
34       * @return an array of the matching strings from the given set
35       */
36      public static String[] prefixSet(final Set<String> set, final String prefix) {
37          final Set<String> prefixSet = new HashSet<>();
38          for (final String str : set) {
39              if (str.startsWith(prefix)) {
40                  prefixSet.add(str);
41              }
42          }
43          return prefixSet.toArray(new String[prefixSet.size()]);
44      }
45  }