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/*******************************************************************************
* Copyright (c) 2007, 2011 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.common.utility.internal;
import java.io.Serializable;
import org.eclipse.jpt.common.utility.Filter;
/**
* Used by various "pluggable" classes to filter objects
* in both directions.
*
* If anyone can come up with a better class name
* and/or method name, I would love to hear it. ~bjv
*/
public interface BidiFilter<T>
extends Filter<T>
{
/**
* Return whether the specified object is "accepted" by the
* "reverse" filter. What that means is determined by the client.
*/
boolean reverseAccept(T o);
final class Null<S>
implements BidiFilter<S>, Serializable
{
@SuppressWarnings("rawtypes")
public static final BidiFilter INSTANCE = new Null();
@SuppressWarnings("unchecked")
public static <R> BidiFilter<R> instance() {
return INSTANCE;
}
// ensure single instance
private Null() {
super();
}
// nothing is filtered - everything is accepted
public boolean accept(S o) {
return true;
}
// nothing is "reverse-filtered" - everything is accepted
public boolean reverseAccept(S o) {
return true;
}
@Override
public String toString() {
return StringTools.buildSingletonToString(this);
}
private static final long serialVersionUID = 1L;
private Object readResolve() {
// replace this object with the singleton
return INSTANCE;
}
}
final class Opaque<S>
implements BidiFilter<S>, Serializable
{
@SuppressWarnings("rawtypes")
public static final BidiFilter INSTANCE = new Opaque();
@SuppressWarnings("unchecked")
public static <R> BidiFilter<R> instance() {
return INSTANCE;
}
// ensure single instance
private Opaque() {
super();
}
// everything is filtered - nothing is accepted
public boolean accept(S o) {
return false;
}
// everything is "reverse-filtered" - nothing is accepted
public boolean reverseAccept(S o) {
return false;
}
@Override
public String toString() {
return StringTools.buildSingletonToString(this);
}
private static final long serialVersionUID = 1L;
private Object readResolve() {
// replace this object with the singleton
return INSTANCE;
}
}
final class Disabled<S>
implements BidiFilter<S>, Serializable
{
@SuppressWarnings("rawtypes")
public static final BidiFilter INSTANCE = new Disabled();
@SuppressWarnings("unchecked")
public static <R> BidiFilter<R> instance() {
return INSTANCE;
}
// ensure single instance
private Disabled() {
super();
}
// throw an exception
public boolean accept(S o) {
throw new UnsupportedOperationException();
}
// throw an exception
public boolean reverseAccept(S o) {
throw new UnsupportedOperationException();
}
@Override
public String toString() {
return StringTools.buildSingletonToString(this);
}
private static final long serialVersionUID = 1L;
private Object readResolve() {
// replace this object with the singleton
return INSTANCE;
}
}
}
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