    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
    018package org.apache.commons.collections4.properties;
    019
    020import java.util.ArrayList;
    021import java.util.Collections;
    022import java.util.Enumeration;
    023import java.util.List;
    024import java.util.Properties;
    025import java.util.Set;
    026
    027import org.apache.commons.collections4.iterators.IteratorEnumeration;
    028
    029/**
    030 * A drop-in replacement for {@link Properties} for sorting keys.
    031 * <p>
    032 * Overrides {@link Properties#keys()} to sort keys. Allows other methods on the superclass to work with sorted keys.
    033 * </p>
    034 *
    035 * @since 4.2
    036 */
    037public class SortedProperties extends Properties {
    038
    039    private static final long serialVersionUID = 1L;
    040
    041    @Override
    042    public synchronized Enumeration<Object> keys() {
    043        final Set<Object> keySet = keySet();
    044        final List<String> keys = new ArrayList<>(keySet.size());
    045        for (final Object key : keySet) {
    046            keys.add(key.toString());
    047        }
    048        Collections.sort(keys);
    049        return new IteratorEnumeration<>(keys.iterator());
    050    }
    051}