/*
* Copyright 2002-2008 the original author or authors.
*
* Licensed 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.springframework.util.comparator;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import org.springframework.util.Assert;
/**
* A comparator that chains a sequence of one or more more Comparators.
*
* <p>A compound comparator calls each Comparator in sequence until a single
* Comparator returns a non-zero result, or the comparators are exhausted and
* zero is returned.
*
* <p>This facilitates in-memory sorting similar to multi-column sorting in SQL.
* The order of any single Comparator in the list can also be reversed.
*
* @author Keith Donald
* @author Juergen Hoeller
* @since 1.2.2
*/
public class CompoundComparator<T> implements Comparator<T>, Serializable {
private final List<InvertibleComparator<T>> comparators;
/**
* Construct a CompoundComparator with initially no Comparators. Clients
* must add at least one Comparator before calling the compare method or an
* IllegalStateException is thrown.
*/
public CompoundComparator() {
this.comparators = new ArrayList<InvertibleComparator<T>>();
}
/**
* Construct a CompoundComparator from the Comparators in the provided array.
* <p>All Comparators will default to ascending sort order,
* unless they are InvertibleComparators.
* @param comparators the comparators to build into a compound comparator
* @see InvertibleComparator
*/
public CompoundComparator(Comparator[] comparators) {
this.comparators = new ArrayList<InvertibleComparator<T>>(comparators.length);
for (Comparator<T> comparator : comparators) {
addComparator(comparator);
}
}
/**
* Add a Comparator to the end of the chain.
* <p>The Comparator will default to ascending sort order,
* unless it is a InvertibleComparator.
* @param comparator the Comparator to add to the end of the chain
* @see InvertibleComparator
*/
public void addComparator(Comparator<T> comparator) {
if (comparator instanceof InvertibleComparator) {
this.comparators.add((InvertibleComparator<T>) comparator);
}
else {
this.comparators.add(new InvertibleComparator<T>(comparator));
}
}
/**
* Add a Comparator to the end of the chain using the provided sort order.
* @param comparator the Comparator to add to the end of the chain
* @param ascending the sort order: ascending (true) or descending (false)
*/
public void addComparator(Comparator<T> comparator, boolean ascending) {
this.comparators.add(new InvertibleComparator<T>(comparator, ascending));
}
/**
* Replace the Comparator at the given index.
* <p>The Comparator will default to ascending sort order,
* unless it is a InvertibleComparator.
* @param index the index of the Comparator to replace
* @param comparator the Comparator to place at the given index
* @see InvertibleComparator
*/
public void setComparator(int index, Comparator<T> comparator) {
if (comparator instanceof InvertibleComparator) {
this.comparators.set(index, (InvertibleComparator<T>) comparator);
}
else {
this.comparators.set(index, new InvertibleComparator<T>(comparator));
}
}
/**
* Replace the Comparator at the given index using the given sort order.
* @param index the index of the Comparator to replace
* @param comparator the Comparator to place at the given index
* @param ascending the sort order: ascending (true) or descending (false)
*/
public void setComparator(int index, Comparator<T> comparator, boolean ascending) {
this.comparators.set(index, new InvertibleComparator<T>(comparator, ascending));
}
/**
* Invert the sort order of each sort definition contained by this compound
* comparator.
*/
public void invertOrder() {
for (InvertibleComparator comparator : this.comparators) {
comparator.invertOrder();
}
}
/**
* Invert the sort order of the sort definition at the specified index.
* @param index the index of the comparator to invert
*/
public void invertOrder(int index) {
this.comparators.get(index).invertOrder();
}
/**
* Change the sort order at the given index to ascending.
* @param index the index of the comparator to change
*/
public void setAscendingOrder(int index) {
this.comparators.get(index).setAscending(true);
}
/**
* Change the sort order at the given index to descending sort.
* @param index the index of the comparator to change
*/
public void setDescendingOrder(int index) {
this.comparators.get(index).setAscending(false);
}
/**
* Returns the number of aggregated comparators.
*/
public int getComparatorCount() {
return this.comparators.size();
}
public int compare(T o1, T o2) {
Assert.state(this.comparators.size() > 0,
"No sort definitions have been added to this CompoundComparator to compare");
for (InvertibleComparator<T> comparator : this.comparators) {
int result = comparator.compare(o1, o2);
if (result != 0) {
return result;
}
}
return 0;
}
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (!(obj instanceof CompoundComparator)) {
return false;
}
CompoundComparator other = (CompoundComparator) obj;
return this.comparators.equals(other.comparators);
}
@Override
public int hashCode() {
return this.comparators.hashCode();
}
@Override
public String toString() {
return "CompoundComparator: " + this.comparators;
}
}
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