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/*******************************************************************************
* Copyright (c) 2007, 2008 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;
import org.eclipse.jpt.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> {
@SuppressWarnings("unchecked")
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 next) {
return true;
}
// nothing is "reverse-filtered" - everything is accepted
public boolean reverseAccept(S o) {
return true;
}
@Override
public String toString() {
return "BidiFilter.Null";
}
}
final class Disabled<S> implements BidiFilter<S> {
@SuppressWarnings("unchecked")
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 next) {
throw new UnsupportedOperationException();
}
// throw an exception
public boolean reverseAccept(S o) {
throw new UnsupportedOperationException();
}
@Override
public String toString() {
return "BidiFilter.Disabled";
}
}
}
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