    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.log4j.helpers;
    018
    019    import java.util.Enumeration;
    020    import java.util.NoSuchElementException;
    021
    022    /**
    023     * An always-empty Enumerator.
    024     *
    025     * @since version 1.0
    026     */
    027    @SuppressWarnings("rawtypes")
    028    public final class NullEnumeration implements Enumeration {
    029        private static final NullEnumeration INSTANCE = new NullEnumeration();
    030
    031        private NullEnumeration() {
    032        }
    033
    034        public static NullEnumeration getInstance() {
    035            return INSTANCE;
    036        }
    037
    038        @Override
    039        public boolean hasMoreElements() {
    040            return false;
    041        }
    042
    043        @Override
    044        public Object nextElement() {
    045            throw new NoSuchElementException();
    046        }
    047    }