Draft proposal: allow the use of relational operators on Comparable classes (original) (raw)

Reinier Zwitserloot reinier at zwitserloot.com
Tue Mar 10 17:03:53 PDT 2009

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--Reinier Zwitserloot

On Mar 10, 2009, at 17:21, Neal Gafter wrote:

This proposal is incompatible with the existing behavior of the comparison operators on the boxed value classes, particularly for Float and Double.

I'll help Neal out and be a bit more verbose:

Existing behaviour unboxes first, which also means that you get type
promotion to make parts fit. You can do this:

Float x = 10.0; Double y = 12.0;

if ( x < y ) /* stuff */;

but you can not call x.compareTo(y), or y.compareTo(x). (AFAIK - it
would be nice if someone tests this theory. Don't have a javac
available at the moment).

Easily fixed in the proposal by stating: If the operation would
succeed under old unboxing rules, use those.

After all, there are ambiguous rules regarding == as well (if I == two
autoboxed values, is it reference comparison, or an equals check)? A
choice was made there too.

On Tue, Mar 10, 2009 at 9:09 AM, Vilya Harvey <vilya.harvey at gmail.com> wrote:

I've attached a draft of a proposal to allow classes which implement the Comparable interface to be used as operands for the relational operators. So for example if you had two Strings, a and b, you would be able to write

if (a < b) { ... } instead of if (a.compareTo(b) < 0) { ... } and you could do the same with your own classes as well. Thanks in advance for any feedback, Vil.

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