| /* EmptyEnumeration.java -- a constant empty enumeration |
| Copyright (C) 2001, 2002 Free Software Foundation, Inc. |
| |
| This file is part of GNU Classpath. |
| |
| GNU Classpath is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2, or (at your option) |
| any later version. |
| |
| GNU Classpath is distributed in the hope that it will be useful, but |
| WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GNU Classpath; see the file COPYING. If not, write to the |
| Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
| 02110-1301 USA. |
| |
| Linking this library statically or dynamically with other modules is |
| making a combined work based on this library. Thus, the terms and |
| conditions of the GNU General Public License cover the whole |
| combination. |
| |
| As a special exception, the copyright holders of this library give you |
| permission to link this library with independent modules to produce an |
| executable, regardless of the license terms of these independent |
| modules, and to copy and distribute the resulting executable under |
| terms of your choice, provided that you also meet, for each linked |
| independent module, the terms and conditions of the license of that |
| module. An independent module is a module which is not derived from |
| or based on this library. If you modify this library, you may extend |
| this exception to your version of the library, but you are not |
| obligated to do so. If you do not wish to do so, delete this |
| exception statement from your version. */ |
| |
| package gnu.java.util; |
| |
| import java.io.Serializable; |
| import java.util.Enumeration; |
| import java.util.NoSuchElementException; |
| |
| /** |
| * This is a helper class that produces an empty Enumerations. There is only |
| * one instance of this class that can be used whenever one needs a |
| * non-null but empty enumeration. Using this class prevents multiple |
| * small objects and inner classes. <code>getInstance()</code> returns |
| * the only instance of this class. It can be shared by multiple objects and |
| * threads. |
| * |
| * @author Mark Wielaard (mark@klomp.org) |
| */ |
| public final class EmptyEnumeration implements Enumeration, Serializable |
| { |
| /** The only instance of this class */ |
| private static final EmptyEnumeration instance = new EmptyEnumeration(); |
| |
| /** |
| * Private constructor that creates a new empty Enumeration. |
| */ |
| private EmptyEnumeration() |
| { |
| } |
| |
| /** |
| * Returns the only instance of this class. |
| * It can be shared by multiple objects and threads. |
| * |
| * @return the common empty enumeration |
| */ |
| public static EmptyEnumeration getInstance() |
| { |
| return instance; |
| } |
| |
| /** |
| * Returns false, since there are no elements. |
| * |
| * @return false |
| */ |
| public boolean hasMoreElements() |
| { |
| return false; |
| } |
| |
| /** |
| * Always throws <code>NoSuchElementException</code>, since it is empty. |
| * |
| * @throws NoSuchElementException this is empty |
| */ |
| public Object nextElement() |
| { |
| throw new NoSuchElementException(); |
| } |
| } |