RE: [Collections] ComparableComparator - nulls OK

2002-06-11 Thread Stephen Colebourne 

-  Original message 
From: Jack, Paul [EMAIL PROTECTED]
  I too like the ComparatorUtils concept outlined below.
  However, we might
  want to consider whether the method names are nullFirst(Comparator) or
  nullFirstComparator(Comparator) etc. I raise this because
  PredicateUtils
  uses the latter at the moment, and it would be nice to be
  consistent (we
  could change PredicateUtils if required).

 Hm.  I always favor shorter names, especially when the longer
 names are redundant...the ComparatorUtils I submitted uses the
 shorter names...

 What do you think of
 Set predicate(Set set, Predicate predicate)
 ?  Is that too nondescript?

Actually, there is another factor involved. The java.utils.Collections class
uses the long form, eg.
Collections.unmodifiableMap(Map);

Thus I would prefer the long form. We could agree to differ from Sun
however, in which case I would submit a patch to the Predicate code.

Stephen


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RE: [Collections] ComparableComparator - nulls OK

2002-06-10 Thread Jack, Paul 

 I too like the ComparatorUtils concept outlined below. 
 However, we might
 want to consider whether the method names are nullFirst(Comparator) or
 nullFirstComparator(Comparator) etc. I raise this because 
 PredicateUtils
 uses the latter at the moment, and it would be nice to be 
 consistent (we
 could change PredicateUtils if required).

Hm.  I always favor shorter names, especially when the longer
names are redundant...the ComparatorUtils I submitted uses the
shorter names...

What do you think of 

Set predicate(Set set, Predicate predicate)

?  Is that too nondescript?

-Paul

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Re: [Collections] ComparableComparator - nulls OK

2002-06-08 Thread Stephen Colebourne 

I too like the ComparatorUtils concept outlined below. However, we might
want to consider whether the method names are nullFirst(Comparator) or
nullFirstComparator(Comparator) etc. I raise this because PredicateUtils
uses the latter at the moment, and it would be nice to be consistent (we
could change PredicateUtils if required).

Stephen

- Original Message -
From: Jack, Paul [EMAIL PROTECTED]
To: 'Jakarta Commons Developers List' [EMAIL PROTECTED]
Sent: Friday, June 07, 2002 9:09 PM
Subject: RE: [Collections] ComparableComparator - nulls OK


 I like the idea of having the functionality provided by
 NullFirstComparator and NullLastComparator, but I have an
 additional suggestion.

 Currently, all of the classes in the comparators subpackage
 are simple, and very useful.  However, it seems that they'd
 most often be used in conjunction with each other; typically,
 I'd use ReverseComparator with ComparableComparator to get
 reverse natural ordering, and I'd probably use a NullSomething
 comparator with ComparableComparator to get natural ordering
 that accepts nulls.

 So my suggestion is, can we fold these all into one static
 utility API?  It would make them much more convenient, IMHO.
 I'm thinking of something like:

 public class ComparatorUtils {

 // same as ComparableComparator.getInstance
 public static Comparator NATURAL;

 public static Comparator nullFirst(Comparator c);
 public static Comparator nullLast(Comparator c);

 // same as reverseComparator
 public static Comparator reverse(Comparator c);

 public static Comparator bean(Comparator c, String getterName);
 public static Comparator transform(Comparator c, Transformer t);

 }

 Also, there are operations involving Comparators that I use
 frequently that would be nice to have in the API:

 public static Object min(Object o1, Object o2, Comparator c);
 public static Object max(Object o1, Object o2, Comparator c);

 which would return the higher or lower of the given objects
 according to the comparator.

 Any of this make sense?

 -Paul



  -Original Message-
  From: Michael A. Smith [mailto:[EMAIL PROTECTED]]
  Sent: Friday, June 07, 2002 1:00 PM
  To: Jakarta Commons Developers List
  Subject: RE: [Collections] ComparableComparator - nulls OK
 
 
  On Fri, 7 Jun 2002, Eric Pugh wrote:
   +1,  In my sorts, having to deal with nulls is causing me
  difficulties as
   well..  Although I could see something like any nulls being
  ignored as a
   type of behavior..  Sort everything, and drop the nulls!
 
  consider:  Comparator.compare(null, x);
 
  how do you drop or ignore the null when doing this compare?
 
 
   -Original Message-
   From: Jonathan Carlson [mailto:[EMAIL PROTECTED]]
   Sent: Friday, June 07, 2002 3:38 PM
   To: [EMAIL PROTECTED]
   Subject: [Collections] ComparableComparator - nulls OK
  
  
   I'd like to make the case for a ComparableComparator that
   allows the sorting of nulls to the bottom.  This could be a
   flag to set on the existing class or another Comparator
   called something like NullableComparableComparator (or
   ComparableNullComparator?).
 
  How about something like this:
 
  public class NullFirstComparator implements Comparator {
private Comparator c;
public NullFirstComparator(Comparator nonNullComparator) {
  this.c = nonNullComparator;
}
public int compare(Object a, Object b) {
  if(a == b) return 0;
  if(a == null) return -1;
  if(b == null) return 1;
  return c.compare(a,b);
}
  }
 
  and
 
  public class NullLastComparator implements Comparator {
private Comparator c;
public NullLastComparator(Comparator nonNullComparator) {
  this.c = nonNullComparator;
}
public int compare(Object a, Object b) {
  if(a == b) return 0;
  if(a == null) return 1;
  if(b == null) return -1;
  return c.compare(a,b);
}
  }
 
 
  That allows you to adjust the behavior of comparison to null for any
  comparator and not just the ComparableComparator.  It sounds like in
  your case (sorting nulls last using ComparableComparator), you'd use:
 
 new NullLastComparator(ComparableComparator.getInstance())
 
 
  If that sounds reasonable, I'll add a full implementation
  (with a better
  Comparator.equals method) to the list of things on my todo list.
 
  regards,
  michael
 
  p.s.  I just threw together the above implementations. I
  wouldn't trust
  it to actually sort things properly (or even compile) -- I may have
  things reversed or something where nulls go first instead of last and
  vice-versa.
 
 
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RE: [Collections] ComparableComparator - nulls OK

2002-06-07 Thread Eric Pugh 

+1,  In my sorts, having to deal with nulls is causing me difficulties as
well..  Although I could see something like any nulls being ignored as a
type of behavior..  Sort everything, and drop the nulls!

Eric

-Original Message-
From: Jonathan Carlson [mailto:[EMAIL PROTECTED]]
Sent: Friday, June 07, 2002 3:38 PM
To: [EMAIL PROTECTED]
Subject: [Collections] ComparableComparator - nulls OK


I'd like to make the case for a ComparableComparator that
allows the sorting of nulls to the bottom.  This could be a
flag to set on the existing class or another Comparator
called something like NullableComparableComparator (or
ComparableNullComparator?).

This becomes a big issue when sorting a collection of
things based on one of their getter methods with generic
components like the TransformingComparator I just
submitted.  Too often the returned value can be a null.

It's not too hard to write my own (I already have), but I
prefer having things like this standardized in one library
rather than written differently for each project.

My two cents.  I'd appreciate feedback, even negative
feedback if it's appropriate.

Jonathan

=
Jonathan Carlson
[EMAIL PROTECTED]
Minneapolis, Minnesota

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RE: [Collections] ComparableComparator - nulls OK

2002-06-07 Thread Jonathan Carlson 

I can't think of a how nulls could be dropped.  The
Comparator API only allows for returning a -1, 0, or +1. 
But thanks for the support for the option of sorting nulls
to the bottom.

Jonathan


=
Jonathan Carlson
[EMAIL PROTECTED]
Minneapolis, Minnesota

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RE: [Collections] ComparableComparator - nulls OK

2002-06-07 Thread Tim Moore 

I don't think that there's any obvious ordering for null and x (or
some other arbitrary object)...I would be inclined to throw an exception
if null is passed in.  If you're sorting a list with nulls, it's
probably best to filter them out before sorting.  I definitely give a
(non-binding) -1 to any kind of special case null handling.

-- 
Tim Moore / Blackboard Inc. / Software Engineer
1899 L Street, NW / 5th Floor / Washington, DC 20036
Phone 202-463-4860 ext. 258 / Fax 202-463-4863


 -Original Message-
 From: Michael A. Smith [mailto:[EMAIL PROTECTED]] 
 Sent: Friday, June 07, 2002 4:00 PM
 To: Jakarta Commons Developers List
 Subject: RE: [Collections] ComparableComparator - nulls OK
 
 
 On Fri, 7 Jun 2002, Eric Pugh wrote:
  +1,  In my sorts, having to deal with nulls is causing me 
 difficulties 
  +as
  well..  Although I could see something like any nulls being 
 ignored as 
  a type of behavior..  Sort everything, and drop the nulls!
 
 consider:  Comparator.compare(null, x);
 
 how do you drop or ignore the null when doing this compare?
 
 
  -Original Message-
  From: Jonathan Carlson [mailto:[EMAIL PROTECTED]]
  Sent: Friday, June 07, 2002 3:38 PM
  To: [EMAIL PROTECTED]
  Subject: [Collections] ComparableComparator - nulls OK
  
  
  I'd like to make the case for a ComparableComparator that 
 allows the 
  sorting of nulls to the bottom.  This could be a flag to set on the 
  existing class or another Comparator called something like 
  NullableComparableComparator (or ComparableNullComparator?).
 
 How about something like this:
 
 public class NullFirstComparator implements Comparator {
   private Comparator c;
   public NullFirstComparator(Comparator nonNullComparator) {
 this.c = nonNullComparator;
   }
   public int compare(Object a, Object b) {
 if(a == b) return 0;
 if(a == null) return -1;
 if(b == null) return 1;
 return c.compare(a,b);
   }
 }
 
 and
 
 public class NullLastComparator implements Comparator {
   private Comparator c;
   public NullLastComparator(Comparator nonNullComparator) {
 this.c = nonNullComparator;
   }
   public int compare(Object a, Object b) {
 if(a == b) return 0;
 if(a == null) return 1;
 if(b == null) return -1;
 return c.compare(a,b);
   }
 }
 
 
 That allows you to adjust the behavior of comparison to null for any 
 comparator and not just the ComparableComparator.  It sounds like in 
 your case (sorting nulls last using ComparableComparator), you'd use:
 
new NullLastComparator(ComparableComparator.getInstance())
 
 
 If that sounds reasonable, I'll add a full implementation 
 (with a better 
 Comparator.equals method) to the list of things on my todo list. 
 
 regards,
 michael
 
 p.s.  I just threw together the above implementations. I 
 wouldn't trust it to actually sort things properly (or even 
 compile) -- I may have things reversed or something where 
 nulls go first instead of last and vice-versa.
 
 
 --
 To unsubscribe, e-mail:   
 mailto:commons-dev- [EMAIL PROTECTED]
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 additional commands, 
 e-mail: mailto:[EMAIL PROTECTED]
 
 

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RE: [Collections] ComparableComparator - nulls OK

2002-06-07 Thread Henri Yandell 

I'm +1 on sorting to the bottom. Would it harm for this to be a default?
ie) no ClassCastException anymore?

On Fri, 7 Jun 2002, Jonathan Carlson wrote:

 I can't think of a how nulls could be dropped.  The
 Comparator API only allows for returning a -1, 0, or +1.
 But thanks for the support for the option of sorting nulls
 to the bottom.

 Jonathan


 =
 Jonathan Carlson
 [EMAIL PROTECTED]
 Minneapolis, Minnesota

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RE: [Collections] ComparableComparator - nulls OK

2002-06-07 Thread Jack, Paul 

I like the idea of having the functionality provided by 
NullFirstComparator and NullLastComparator, but I have an
additional suggestion.

Currently, all of the classes in the comparators subpackage
are simple, and very useful.  However, it seems that they'd
most often be used in conjunction with each other; typically,
I'd use ReverseComparator with ComparableComparator to get
reverse natural ordering, and I'd probably use a NullSomething
comparator with ComparableComparator to get natural ordering
that accepts nulls.

So my suggestion is, can we fold these all into one static
utility API?  It would make them much more convenient, IMHO.
I'm thinking of something like:

public class ComparatorUtils {

// same as ComparableComparator.getInstance
public static Comparator NATURAL;

public static Comparator nullFirst(Comparator c);
public static Comparator nullLast(Comparator c);

// same as reverseComparator
public static Comparator reverse(Comparator c);

public static Comparator bean(Comparator c, String getterName);
public static Comparator transform(Comparator c, Transformer t);

}

Also, there are operations involving Comparators that I use 
frequently that would be nice to have in the API:

public static Object min(Object o1, Object o2, Comparator c);
public static Object max(Object o1, Object o2, Comparator c);

which would return the higher or lower of the given objects 
according to the comparator.

Any of this make sense?

-Paul



 -Original Message-
 From: Michael A. Smith [mailto:[EMAIL PROTECTED]]
 Sent: Friday, June 07, 2002 1:00 PM
 To: Jakarta Commons Developers List
 Subject: RE: [Collections] ComparableComparator - nulls OK
 
 
 On Fri, 7 Jun 2002, Eric Pugh wrote:
  +1,  In my sorts, having to deal with nulls is causing me 
 difficulties as
  well..  Although I could see something like any nulls being 
 ignored as a
  type of behavior..  Sort everything, and drop the nulls!
 
 consider:  Comparator.compare(null, x);
 
 how do you drop or ignore the null when doing this compare?
 
 
  -Original Message-
  From: Jonathan Carlson [mailto:[EMAIL PROTECTED]]
  Sent: Friday, June 07, 2002 3:38 PM
  To: [EMAIL PROTECTED]
  Subject: [Collections] ComparableComparator - nulls OK
  
  
  I'd like to make the case for a ComparableComparator that
  allows the sorting of nulls to the bottom.  This could be a
  flag to set on the existing class or another Comparator
  called something like NullableComparableComparator (or
  ComparableNullComparator?).
 
 How about something like this:
 
 public class NullFirstComparator implements Comparator {
   private Comparator c;
   public NullFirstComparator(Comparator nonNullComparator) {
 this.c = nonNullComparator;
   }
   public int compare(Object a, Object b) {
 if(a == b) return 0;
 if(a == null) return -1;
 if(b == null) return 1;
 return c.compare(a,b);
   }
 }
 
 and
 
 public class NullLastComparator implements Comparator {
   private Comparator c;
   public NullLastComparator(Comparator nonNullComparator) {
 this.c = nonNullComparator;
   }
   public int compare(Object a, Object b) {
 if(a == b) return 0;
 if(a == null) return 1;
 if(b == null) return -1;
 return c.compare(a,b);
   }
 }
 
 
 That allows you to adjust the behavior of comparison to null for any 
 comparator and not just the ComparableComparator.  It sounds like in 
 your case (sorting nulls last using ComparableComparator), you'd use:
 
new NullLastComparator(ComparableComparator.getInstance())
 
 
 If that sounds reasonable, I'll add a full implementation 
 (with a better 
 Comparator.equals method) to the list of things on my todo list. 
 
 regards,
 michael
 
 p.s.  I just threw together the above implementations. I 
 wouldn't trust
 it to actually sort things properly (or even compile) -- I may have
 things reversed or something where nulls go first instead of last and
 vice-versa.
 
 
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 To unsubscribe, e-mail:   
 mailto:[EMAIL PROTECTED]
 For additional commands, e-mail: 
 mailto:[EMAIL PROTECTED]
 

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