/*
* 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 compare method.
This class is Serializable from Commons Collections 4.0.
Type parameters: See Also: Since: 2.1
/**
* 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.
* <p>
* This class is Serializable from Commons Collections 4.0.
* </p>
*
* @param <I> the input type to the transformer
* @param <O> 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<I, O> implements Comparator<I>, Serializable {
Serialization version from Collections 4.0. /** Serialization version from Collections 4.0. */
private static final long serialVersionUID = 3456940356043606220L;
The decorated comparator. /** The decorated comparator. */
private final Comparator<O> decorated;
The transformer being used. /** The transformer being used. */
private final Transformer<? super I, ? extends O> transformer;
//-----------------------------------------------------------------------
Constructs an instance with the given Transformer and a ComparableComparator. Params: - transformer – what will transform the arguments to
compare
/**
* Constructs an instance with the given Transformer and a
* {@link ComparableComparator ComparableComparator}.
*
* @param transformer what will transform the arguments to <code>compare</code>
*/
public TransformingComparator(final Transformer<? super I, ? extends O> transformer) {
this(transformer, ComparatorUtils.NATURAL_COMPARATOR);
}
Constructs an instance with the given Transformer and Comparator.
Params: - transformer – what will transform the arguments to
compare - decorated – the decorated Comparator
/**
* Constructs an instance with the given Transformer and Comparator.
*
* @param transformer what will transform the arguments to <code>compare</code>
* @param decorated the decorated Comparator
*/
public TransformingComparator(final Transformer<? super I, ? extends O> transformer,
final Comparator<O> decorated) {
this.decorated = decorated;
this.transformer = transformer;
}
//-----------------------------------------------------------------------
Returns the result of comparing the values from the transform operation.
Params: - obj1 – the first object to transform then compare
- obj2 – the second object to transform then compare
Returns: negative if obj1 is less, positive if greater, zero if equal
/**
* 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 equals. Returns: a hash code for this comparator.
/**
* 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 Comparator whose ordering is known to be equivalent to mine.
This implementation returns true
iff that is a TransformingComparator whose attributes are equal to mine.
Params: - object – the object to compare to
Returns: true if equal
/**
* Returns <code>true</code> iff <i>that</i> Object is
* is a {@link Comparator} whose ordering is known to be
* equivalent to mine.
* <p>
* This implementation returns <code>true</code>
* iff <code><i>that</i></code> 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;
}
}