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Simplifying ComparatorChain version from the version taken from Commons Collections. The ability to modify the comparator list, and the ability to reverse items (rather than simply wrapping in ReverseComparator) was complexity inducing. Also added a unit test. 

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/lang/trunk@1167671 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Henri Yandell 2011-09-11 05:07:14 +00:00
parent dc3bef79c8
commit 2fcc80e71f
2 changed files with 65 additions and 198 deletions
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209
src/main/java/org/apache/commons/lang3/compare/ComparatorChain.java
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@ -18,7 +18,7 @@ package org.apache.commons.lang3.compare;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.BitSet;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
@ -35,16 +35,6 @@ import java.util.List;
* allows Java classes to emulate that kind of behaviour
* when sorting a List.</p>
*
* <p>To further facilitate SQL-like sorting, the order of
* any single Comparator in the list can be reversed.</p>
*
* <p>Calling a method that adds new Comparators or
* changes the ascend/descend sort <i>after compare(Object,
* Object) has been called</i> will result in an
* UnsupportedOperationException. However, <i>take care</i>
* to not alter the underlying List of Comparators
* or the BitSet that defines the sort order.</p>
*
* <p>Instances of ComparatorChain are not synchronized.
* The class is not thread-safe at construction time, but
* it <i>is</i> thread-safe to perform multiple comparisons
@ -55,51 +45,19 @@ import java.util.List;
*/
public class ComparatorChain<E> implements Comparator<E>, Serializable {
/** Serialization version from Collections 2.0. */
private static final long serialVersionUID = -721644942746081630L;
/** The list of comparators in the chain. */
protected List<Comparator<E>> comparatorChain = null;
/** Order - false (clear) = ascend; true (set) = descend. */
protected BitSet orderingBits = null;
/** Whether the chain has been "locked". */
protected boolean isLocked = false;
//-----------------------------------------------------------------------
/**
* Construct a ComparatorChain with no Comparators.
* You must add at least one Comparator before calling
* the compare(Object,Object) method, or an
* UnsupportedOperationException is thrown
*/
public ComparatorChain() {
this(new ArrayList<Comparator<E>>(), new BitSet());
}
/**
* Construct a ComparatorChain with a single Comparator,
* sorting in the forward order
*
* @param comparator First comparator in the Comparator chain
*/
public ComparatorChain(Comparator<E> comparator) {
this(comparator, false);
}
/**
* Construct a Comparator chain with a single Comparator,
* sorting in the given order
*
* @param comparator First Comparator in the ComparatorChain
* @param reverse false = forward sort; true = reverse sort
*/
public ComparatorChain(Comparator<E> comparator, boolean reverse) {
comparatorChain = new ArrayList<Comparator<E>>(1);
comparatorChain.add(comparator);
orderingBits = new BitSet(1);
if (reverse == true) {
orderingBits.set(0);
}
public ComparatorChain(Comparator<E>... comparators) {
this.comparatorChain = new ArrayList<Comparator<E>>();
Collections.addAll(this.comparatorChain, comparators);
}
/**
@ -111,110 +69,11 @@ public class ComparatorChain<E> implements Comparator<E>, Serializable {
* @see #ComparatorChain(List,BitSet)
*/
public ComparatorChain(List<Comparator<E>> list) {
this(list, new BitSet(list.size()));
}
/**
* Construct a ComparatorChain from the Comparators in the
* given List. The sort order of each column will be
* drawn from the given BitSet. When determining the sort
* order for Comparator at index <i>i</i> in the List,
* the ComparatorChain will call BitSet.get(<i>i</i>).
* If that method returns <i>false</i>, the forward
* sort order is used; a return value of <i>true</i>
* indicates reverse sort order.
*
* @param list List of Comparators. NOTE: This constructor does not perform a
* defensive copy of the list
* @param bits Sort order for each Comparator. Extra bits are ignored,
* unless extra Comparators are added by another method.
*/
public ComparatorChain(List<Comparator<E>> list, BitSet bits) {
comparatorChain = list;
orderingBits = bits;
this.comparatorChain = new ArrayList<Comparator<E>>();
this.comparatorChain.addAll(list);
}
//-----------------------------------------------------------------------
/**
* Add a Comparator to the end of the chain using the
* forward sort order
*
* @param comparator Comparator with the forward sort order
*/
public void addComparator(Comparator<E> comparator) {
addComparator(comparator, false);
}
/**
* Add a Comparator to the end of the chain using the
* given sort order
*
* @param comparator Comparator to add to the end of the chain
* @param reverse false = forward sort order; true = reverse sort order
*/
public void addComparator(Comparator<E> comparator, boolean reverse) {
checkLocked();
comparatorChain.add(comparator);
if (reverse == true) {
orderingBits.set(comparatorChain.size() - 1);
}
}
/**
* Replace the Comparator at the given index, maintaining
* the existing sort order.
*
* @param index index of the Comparator to replace
* @param comparator Comparator to place at the given index
* @exception IndexOutOfBoundsException
* if index &lt; 0 or index &gt;= size()
*/
public void setComparator(int index, Comparator<E> comparator) throws IndexOutOfBoundsException {
setComparator(index, comparator, false);
}
/**
* Replace the Comparator at the given index in the
* ComparatorChain, using the given sort order
*
* @param index index of the Comparator to replace
* @param comparator Comparator to set
* @param reverse false = forward sort order; true = reverse sort order
*/
public void setComparator(int index, Comparator<E> comparator, boolean reverse) {
checkLocked();
comparatorChain.set(index,comparator);
if (reverse == true) {
orderingBits.set(index);
} else {
orderingBits.clear(index);
}
}
/**
* Change the sort order at the given index in the
* ComparatorChain to a forward sort.
*
* @param index Index of the ComparatorChain
*/
public void setForwardSort(int index) {
checkLocked();
orderingBits.clear(index);
}
/**
* Change the sort order at the given index in the
* ComparatorChain to a reverse sort.
*
* @param index Index of the ComparatorChain
*/
public void setReverseSort(int index) {
checkLocked();
orderingBits.set(index);
}
/**
* Number of Comparators in the current ComparatorChain.
*
@ -225,47 +84,13 @@ public class ComparatorChain<E> implements Comparator<E>, Serializable {
}
/**
* Determine if modifications can still be made to the
* ComparatorChain. ComparatorChains cannot be modified
* once they have performed a comparison.
*
* @return true = ComparatorChain cannot be modified; false =
* ComparatorChain can still be modified.
*/
public boolean isLocked() {
return isLocked;
}
// throw an exception if the ComparatorChain is locked
private void checkLocked() {
if (isLocked == true) {
throw new UnsupportedOperationException("Comparator ordering cannot be changed after the first comparison is performed");
}
}
private void checkChainIntegrity() {
if (comparatorChain.size() == 0) {
throw new UnsupportedOperationException("ComparatorChains must contain at least one Comparator");
}
}
//-----------------------------------------------------------------------
/**
* Perform comparisons on the Objects as per
* Comparator.compare(o1,o2).
* Perform comparisons on the Objects as per Comparator.compare(o1,o2).
*
* @param o1 the first object to compare
* @param o2 the second object to compare
* @return -1, 0, or 1
* @exception UnsupportedOperationException
* if the ComparatorChain does not contain at least one
* Comparator
*/
public int compare(E o1, E o2) throws UnsupportedOperationException {
if (isLocked == false) {
checkChainIntegrity();
isLocked = true;
}
public int compare(E o1, E o2) {
// iterate over all comparators in the chain
Iterator<Comparator<E>> comparators = comparatorChain.iterator();
@ -274,14 +99,6 @@ public class ComparatorChain<E> implements Comparator<E>, Serializable {
Comparator<E> comparator = comparators.next();
int retval = comparator.compare(o1,o2);
if (retval != 0) {
// invert the order if it is a reverse sort
if (orderingBits.get(comparatorIndex) == true) {
if(Integer.MIN_VALUE == retval) {
retval = Integer.MAX_VALUE;
} else {
retval *= -1;
}
}
return retval;
}
}
@ -301,12 +118,9 @@ public class ComparatorChain<E> implements Comparator<E>, Serializable {
@Override
public int hashCode() {
int hash = 0;
if (null != comparatorChain) {
if (comparatorChain != null) {
hash ^= comparatorChain.hashCode();
}
if (null != orderingBits) {
hash ^= orderingBits.hashCode();
}
return hash;
}
@ -331,13 +145,12 @@ public class ComparatorChain<E> implements Comparator<E>, Serializable {
if (this == object) {
return true;
}
if (null == object) {
if (object == null) {
return false;
}
if (object.getClass().equals(this.getClass())) {
ComparatorChain<?> chain = (ComparatorChain<?>) object;
return ((null == orderingBits ? null == chain.orderingBits : orderingBits
.equals(chain.orderingBits)) && (null == comparatorChain ? null == chain.comparatorChain
return ( (comparatorChain == null ? chain.comparatorChain == null
: comparatorChain.equals(chain.comparatorChain)));
}
return false;

54
src/test/java/org/apache/commons/lang3/compare/ComparatorChainTest.java Normal file
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@ -0,0 +1,54 @@
/*
* 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.lang3.compare;
import static org.junit.Assert.*;
import java.util.Comparator;
import org.junit.Before;
import org.junit.Test;
/**
* <p>
* Tests the methods in the {@link org.apache.commons.lang3.compare.ComparatorChain} class.
* </p>
*
* @version $Id: RangeTest.java 1147537 2011-07-17 06:10:37Z mbenson $
*/
public class ComparatorChainTest {
@Test
public void testUse() {
// Sorts ABC-123 by numbers and then letters
ComparatorChain cc = new ComparatorChain(
new ComparableComparator<String>() {
public int compare(String o1, String o2) {
return super.compare(o1.substring(4), o2.substring(4));
}
},
ComparableComparator.INSTANCE
);
assertTrue("Comparison failed", cc.compare( "ABC-123", "ABC-124" ) < 0 );
assertTrue("Comparison failed", cc.compare( "ZZZ-123", "AAA-124" ) < 0 );
assertTrue("Comparison failed", cc.compare( "ABC-123", "ABD-123" ) < 0 );
assertTrue("Comparison failed", cc.compare( "ABC-123", "ABC-123" ) == 0 );
}
}