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Fix deviation from Comparator contract 

[sgn(compare(x, y)) == -sgn(compare(y, x))]

Eliminate multiplication by switching order of objects passed to
underlying comparator.


git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/collections/trunk@130667 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Michael Smith 2002-03-20 00:25:37 +00:00
parent 96cd122c69
commit d0d74a4e1a
1 changed files with 12 additions and 13 deletions
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21
src/java/org/apache/commons/collections/comparators/ReverseComparator.java
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@ -61,20 +61,19 @@ import java.util.Comparator;
* Reverses the order of another comparator. * Reverses the order of another comparator.
* *
* @author bayard@generationjava.com * @author bayard@generationjava.com
* @version $Id: ReverseComparator.java,v 1.5 2002/03/01 19:18:49 morgand Exp $ * @author <a href="mailto:mas@apache.org">Michael A. Smith</a>
* @version $Id: ReverseComparator.java,v 1.6 2002/03/20 00:25:37 mas Exp $
*/ */
public class ReverseComparator implements Comparator,Serializable { public class ReverseComparator implements Comparator,Serializable {
private Comparator comparator; private Comparator comparator;
/** /**
* Creates a reverse comparator that will invert any List. * Creates a comparator that compares objects based on the inverse of their
* It merely reverses the existing order; it does not * natural ordering.
* reorder the List according to reverse "natural" order.
* In many cases, a faster alternative to this is
* the reverse(List) method of java.util.Collection.
*/ */
public ReverseComparator() { public ReverseComparator() {
this(null);
} }
/** /**
@ -82,15 +81,15 @@ public class ReverseComparator implements Comparator,Serializable {
* of the passed in comparator. * of the passed in comparator.
*/ */
public ReverseComparator(Comparator comparator) { public ReverseComparator(Comparator comparator) {
if(comparator != null) {
this.comparator = comparator; this.comparator = comparator;
} else {
this.comparator = ComparableComparator.getInstance();
}
} }
public int compare(Object o1, Object o2) { public int compare(Object o1, Object o2) {
if(comparator == null) { return comparator.compare(o2, o1);
return -1;
} else {
return -1*comparator.compare(o1,o2);
}
} }
} }