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 */
017package org.apache.logging.log4j.core.util;
018
019import java.util.HashSet;
020import java.util.Set;
021
022/**
023 * Set-related convenience methods.
024 */
025public final class SetUtils {
026    private SetUtils() {
027    }
028
029    /**
030     * Extracts the Strings from a Set that start with a given prefix.
031     *
032     * @param set a Set of Strings (assumed to all be non-{@code null})
033     * @param prefix the prefix to look for in the string set
034     * @return an array of the matching strings from the given set
035     */
036    public static String[] prefixSet(final Set<String> set, final String prefix) {
037        final Set<String> prefixSet = new HashSet<>();
038        for (final String str : set) {
039            if (str.startsWith(prefix)) {
040                prefixSet.add(str);
041            }
042        }
043        return prefixSet.toArray(new String[prefixSet.size()]);
044    }
045}