| /****************************************************************************** |
| * Copyright (c) 2003 IBM Corporation and others. |
| * All rights reserved. This program and the accompanying materials |
| * are made available under the terms of the Eclipse Public License v1.0 |
| * which accompanies this distribution, and is available at |
| * http://www.eclipse.org/legal/epl-v10.html |
| * |
| * Contributors: |
| * IBM Corporation - initial API and implementation |
| ****************************************************************************/ |
| |
| |
| package org.eclipse.gmf.runtime.common.core.util; |
| |
| /** |
| * A specification of classes that implement the <em>Null Object</em> pattern. |
| * Implementors of this interface have a unique instance that represents a |
| * pointer-safe <code>null</code>. The interpretation of <code>null</code> |
| * may vary; it may mean absence of a value, invalid value, etc. |
| * <p> |
| * API clients should <b>not</b> implement this interface. |
| * </p> |
| */ |
| public interface INullObject { |
| |
| /** |
| * Queries whether <code>this</code> is the <code>null</code> instance of a |
| * given implementation class. The <code>null</code> instance must be unique. |
| * |
| * @return <code>true</code> if I am the special "null" instance; |
| * <code>false</code>, otherwise |
| */ |
| boolean isNull(); |
| } |
