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Date: Fri, 26 Aug 2011 01:40:27 -0700
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Subject: Re: [lang] ComparatorChain redesign
From: James Ring <sjr@jdns.org>
To: Commons Developers List <dev@commons.apache.org>
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Google Guava has Ordering:

http://guava-libraries.googlecode.com/svn/trunk/javadoc/com/google/common/c=
ollect/Ordering.html

It is an incredibly useful class. Some random example of how it's awesome:

http://www.polygenelubricants.com/2010/10/elegant-comparison-logic-with-gua=
va.html

Recommend that ComparatorChain.. just do what Ordering does. :)

On Fri, Aug 26, 2011 at 1:17 AM, Henri Yandell <flamefew@gmail.com> wrote:
> Looking at the Collections ComparatorChain class, I think it's overcompli=
cated.
>
> The current API is:
>
> public class ComparatorChain<E> implements Comparator<E>, Serializable {
> =A0 =A0public ComparatorChain() {
> =A0 =A0public ComparatorChain(Comparator<E> comparator) {
> =A0 =A0public ComparatorChain(Comparator<E> comparator, boolean reverse) =
{
> =A0 =A0public ComparatorChain(List<Comparator<E>> list) {
> =A0 =A0public ComparatorChain(List<Comparator<E>> list, BitSet bits) {
> =A0 =A0public void addComparator(Comparator<E> comparator) {
> =A0 =A0public void addComparator(Comparator<E> comparator, boolean revers=
e) {
> =A0 =A0public void setComparator(int index, Comparator<E> comparator)
> throws IndexOutOfBoundsException {
> =A0 =A0public void setComparator(int index, Comparator<E> comparator,
> boolean reverse) {
> =A0 =A0public void setForwardSort(int index) {
> =A0 =A0public void setReverseSort(int index) {
> =A0 =A0public int size() {
> =A0 =A0public boolean isLocked() {
> =A0 =A0public int compare(E o1, E o2) throws UnsupportedOperationExceptio=
n {
> =A0 =A0public int hashCode() {
> =A0 =A0public boolean equals(Object object) {
>
> The whole reverse notion seems like unnecessary duplication. If you
> wanted such you could wrap a ReverseComparator around the comparator
> before adding. I also think the notion of locking should also go away,
> make these immutable objects.
>
> ie:
>
>
> public class ComparatorChain<E> implements Comparator<E>, Serializable {
> =A0 =A0public ComparatorChain(Comparator<E> comparator...) {
> =A0 =A0public ComparatorChain(List<Comparator<E>> list) {
> =A0 =A0public int size() {
> =A0 =A0public int compare(E o1, E o2) {
> =A0 =A0public int hashCode() {
> =A0 =A0public boolean equals(Object object) {
>
> The constructors could throw exceptions when they contain no
> comparator. Or we could simply return 0 as having no comparators is
> the same as the comparators being exhausted.
>
> Any thoughts on the simpler API?
>
> Should it also implement Iterable as a way to loop through the
> contained comparators?
>
> Hen
>
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