| /******************************************************************************* |
| * Copyright (c) 2005, 2007 Oracle. 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: |
| * Oracle - initial API and implementation |
| ******************************************************************************/ |
| package org.eclipse.jpt.utility.internal; |
| |
| /** |
| * Used by various "pluggable" classes to filter objects. |
| */ |
| public interface Filter<T> { |
| |
| /** |
| * Return whether the specified object is "accepted" by the |
| * filter. The semantics of "accept" is determined by the |
| * contract between the client and the server. |
| */ |
| boolean accept(T o); |
| |
| |
| final class Null<S> implements Filter<S> { |
| @SuppressWarnings("unchecked") |
| public static final Filter INSTANCE = new Null(); |
| @SuppressWarnings("unchecked") |
| public static <R> Filter<R> instance() { |
| return INSTANCE; |
| } |
| // ensure single instance |
| private Null() { |
| super(); |
| } |
| // nothing is filtered - everything is accepted |
| public boolean accept(S next) { |
| return true; |
| } |
| @Override |
| public String toString() { |
| return "Filter.Null"; |
| } |
| } |
| |
| } |
