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/*******************************************************************************
* 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 transform objects.
* Transform an object of type T1 to an object of type T2.
*/
public interface Transformer<T1, T2> {
/**
* Return the transformed object.
* The semantics of "transform" is determined by the
* contract between the client and the server.
*/
T2 transform(T1 o);
final class Null<S1, S2> implements Transformer<S1, S2> {
@SuppressWarnings("unchecked")
public static final Transformer INSTANCE = new Null();
@SuppressWarnings("unchecked")
public static <R1, R2> Transformer<R1, R2> instance() {
return INSTANCE;
}
// ensure single instance
private Null() {
super();
}
// simply return the object, unchanged
@SuppressWarnings("unchecked")
public S2 transform(S1 o) {
return (S2) o;
}
@Override
public String toString() {
return "Transformer.Null";
}
}
final class Disabled<S1, S2> implements Transformer<S1, S2> {
@SuppressWarnings("unchecked")
public static final Transformer INSTANCE = new Disabled();
@SuppressWarnings("unchecked")
public static <R1, R2> Transformer<R1, R2> instance() {
return INSTANCE;
}
// ensure single instance
private Disabled() {
super();
}
// throw an exception
public S2 transform(S1 o) {
throw new UnsupportedOperationException();
}
@Override
public String toString() {
return "Transformer.Disabled";
}
}
}
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