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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   *
    24   *
    25   *
    26   */
    27  public final class SetUtils {
    28      private SetUtils() {}
    29
    30      /**
    31       * Extracts the Strings from a Set that start with a given prefix.
    32       *
    33       * @param set    a Set of Strings (assumed to all be non-{@code null})
    34       * @param prefix the prefix to look for in the string set
    35       * @return an array of the matching strings from the given set
    36       */
    37      public static String[] prefixSet(final Set<String> set, final String prefix) {
    38          final Set<String> prefixSet = new HashSet<String>();
    39          for (final String str : set) {
    40              if (str.startsWith(prefix)) {
    41                  prefixSet.add(str);
    42              }
    43          }
    44          return prefixSet.toArray(new String[prefixSet.size()]);
    45      }
    46  }