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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.collections4.comparators;
import java.io.Serializable;
import java.util.Comparator;
import org.apache.commons.collections4.ComparatorUtils;
import org.apache.commons.collections4.Transformer;
/**
* Decorates another Comparator with transformation behavior. That is, the
* return value from the transform operation will be passed to the decorated
* {@link Comparator#compare(Object,Object) compare} method.
*
* This class is Serializable from Commons Collections 4.0.
*
* @param the input type to the transformer
* @param the output type from the transformer
*
* @since 2.1
*
* @see org.apache.commons.collections4.Transformer
* @see org.apache.commons.collections4.comparators.ComparableComparator
*/
public class TransformingComparator implements Comparator, Serializable {
/** Serialization version from Collections 4.0. */
private static final long serialVersionUID = 3456940356043606220L;
/** The decorated comparator. */
private final Comparator decorated;
/** The transformer being used. */
private final Transformer transformer;
//-----------------------------------------------------------------------
/**
* Constructs an instance with the given Transformer and a
* {@link ComparableComparator ComparableComparator}.
*
* @param transformer what will transform the arguments to compare
*/
@SuppressWarnings("unchecked")
public TransformingComparator(final Transformer transformer) {
this(transformer, ComparatorUtils.NATURAL_COMPARATOR);
}
/**
* Constructs an instance with the given Transformer and Comparator.
*
* @param transformer what will transform the arguments to compare
* @param decorated the decorated Comparator
*/
public TransformingComparator(final Transformer transformer,
final Comparator decorated) {
this.decorated = decorated;
this.transformer = transformer;
}
//-----------------------------------------------------------------------
/**
* Returns the result of comparing the values from the transform operation.
*
* @param obj1 the first object to transform then compare
* @param obj2 the second object to transform then compare
* @return negative if obj1 is less, positive if greater, zero if equal
*/
@Override
public int compare(final I obj1, final I obj2) {
final O value1 = this.transformer.transform(obj1);
final O value2 = this.transformer.transform(obj2);
return this.decorated.compare(value1, value2);
}
//-----------------------------------------------------------------------
/**
* Implement a hash code for this comparator that is consistent with
* {@link #equals(Object) equals}.
*
* @return a hash code for this comparator.
*/
@Override
public int hashCode() {
int total = 17;
total = total*37 + (decorated == null ? 0 : decorated.hashCode());
total = total*37 + (transformer == null ? 0 : transformer.hashCode());
return total;
}
/**
* Returns true iff that Object is
* is a {@link Comparator} whose ordering is known to be
* equivalent to mine.
*
* This implementation returns true
* iff that is a {@link TransformingComparator}
* whose attributes are equal to mine.
*
* @param object the object to compare to
* @return true if equal
*/
@Override
public boolean equals(final Object object) {
if (this == object) {
return true;
}
if (null == object) {
return false;
}
if (object.getClass().equals(this.getClass())) {
final TransformingComparator comp = (TransformingComparator) object;
return (null == decorated ? null == comp.decorated : decorated.equals(comp.decorated)) &&
(null == transformer ? null == comp.transformer : transformer.equals(comp.transformer));
}
return false;
}
}