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/*******************************************************************************
* Copyright (c) 2013 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.comparator;
import java.util.Comparator;
import org.eclipse.jpt.common.utility.internal.transformer.TransformationComparator;
import org.eclipse.jpt.common.utility.transformer.Transformer;
/**
* {@link Comparator} utility methods.
*/
public final class ComparatorTools {
// ********** transformation **********
/**
* Return a comparator will transform the elements to be compared and
* compare the resulting outputs (i.e. assume the outputs
* implement the {@link Comparable} interface).
*
* @param <E> the type of elements to be compared
* @param <O> the type of the result of transforming the elements and the type
* of the elements to be compared by the wrapped comaparator, if present
*
* @see TransformationComparator
*/
public static <E, O> Comparator<E> transformationComparator(Transformer<? super E, ? extends O> transformer) {
return transformationComparator(transformer, null);
}
/**
* Return a comparator will transform the elements to be compared and pass the
* resulting outputs to a specified comparator.
* If the specified comparator is <code>null</code>,
* the natural ordering of the outputs will be used (i.e. assume the outputs
* implement the {@link Comparable} interface).
*
* @param <E> the type of elements to be compared
* @param <O> the type of the result of transforming the elements and the type
* of the elements to be compared by the wrapped comaparator, if present
*
* @see TransformationComparator
*/
public static <E, O> Comparator<E> transformationComparator(Transformer<? super E, ? extends O> transformer, Comparator<O> comparator) {
return new TransformationComparator<E, O>(transformer, comparator);
}
// ********** constructor **********
/**
* Suppress default constructor, ensuring non-instantiability.
*/
private ComparatorTools() {
super();
throw new UnsupportedOperationException();
}
}
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