| /******************************************************************************* |
| * Copyright (c) 2005, 2010 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; |
| |
| import java.io.Serializable; |
| |
| /** |
| * Used by various "pluggable" classes to filter objects. |
| * <p> |
| * Provisional API: This interface is part of an interim API that is still |
| * under development and expected to change significantly before reaching |
| * stability. It is available at this early stage to solicit feedback from |
| * pioneering adopters on the understanding that any code that uses this API |
| * will almost certainly be broken (repeatedly) as the API evolves. |
| * |
| * @param <T> the type of objects to be filtered |
| */ |
| 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); |
| |
| |
| /** |
| * Singleton implemetation of the filter interface that accepts all the |
| * objects (i.e. it does no filtering). |
| */ |
| final class Null<S> implements Filter<S>, Serializable { |
| @SuppressWarnings("rawtypes") |
| 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 o) { |
| return true; |
| } |
| @Override |
| public String toString() { |
| return "Filter.Null"; //$NON-NLS-1$ |
| } |
| private static final long serialVersionUID = 1L; |
| private Object readResolve() { |
| // replace this object with the singleton |
| return INSTANCE; |
| } |
| } |
| |
| /** |
| * Singleton implemetation of the filter interface that accepts none of the |
| * objects (i.e. it filters out all the objects). |
| */ |
| final class Opaque<S> implements Filter<S>, Serializable { |
| @SuppressWarnings("rawtypes") |
| public static final Filter INSTANCE = new Opaque(); |
| @SuppressWarnings("unchecked") |
| public static <R> Filter<R> instance() { |
| return INSTANCE; |
| } |
| // ensure single instance |
| private Opaque() { |
| super(); |
| } |
| // everything is filtered - nothing is accepted |
| public boolean accept(S o) { |
| return false; |
| } |
| @Override |
| public String toString() { |
| return "Filter.Opaque"; //$NON-NLS-1$ |
| } |
| private static final long serialVersionUID = 1L; |
| private Object readResolve() { |
| // replace this object with the singleton |
| return INSTANCE; |
| } |
| } |
| |
| /** |
| * Singleton implemetation of the filter interface that throws an exception |
| * if called. |
| */ |
| final class Disabled<S> implements Filter<S>, Serializable { |
| @SuppressWarnings("rawtypes") |
| public static final Filter INSTANCE = new Disabled(); |
| @SuppressWarnings("unchecked") |
| public static <R> Filter<R> instance() { |
| return INSTANCE; |
| } |
| // ensure single instance |
| private Disabled() { |
| super(); |
| } |
| // throw an exception |
| public boolean accept(S o) { |
| throw new UnsupportedOperationException(); |
| } |
| @Override |
| public String toString() { |
| return "Filter.Disabled"; //$NON-NLS-1$ |
| } |
| private static final long serialVersionUID = 1L; |
| private Object readResolve() { |
| // replace this object with the singleton |
| return INSTANCE; |
| } |
| } |
| |
| } |