001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements. See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache license, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License. You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the license for the specific language governing permissions and
015     * limitations under the license.
016     */
017    package org.apache.logging.log4j.core.util;
018    
019    import java.util.HashSet;
020    import java.util.Set;
021    
022    /**
023     *
024     *
025     *
026     */
027    public final class SetUtils {
028        private SetUtils() {}
029    
030        /**
031         * Extracts the Strings from a Set that start with a given prefix.
032         *
033         * @param set    a Set of Strings (assumed to all be non-{@code null})
034         * @param prefix the prefix to look for in the string set
035         * @return an array of the matching strings from the given set
036         */
037        public static String[] prefixSet(final Set<String> set, final String prefix) {
038            final Set<String> prefixSet = new HashSet<String>();
039            for (final String str : set) {
040                if (str.startsWith(prefix)) {
041                    prefixSet.add(str);
042                }
043            }
044            return prefixSet.toArray(new String[prefixSet.size()]);
045        }
046    }