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 public class NullEnumeration implements Enumeration { 028 private static final NullEnumeration instance = new NullEnumeration(); 029 030 private NullEnumeration() { 031 } 032 033 public static NullEnumeration getInstance() { 034 return instance; 035 } 036 037 public boolean hasMoreElements() { 038 return false; 039 } 040 041 public Object nextElement() { 042 throw new NoSuchElementException(); 043 } 044 }