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    }