Proposal: Comparables.isCommutativelyComparable (original) (raw)

Martin Buchholz martinrb at google.com
Sun Jun 9 01:20:54 UTC 2013

On Sat, Jun 8, 2013 at 8:50 AM, Doug Lea <dl at cs.oswego.edu> wrote:

But there's nothing about interface Comparable that forces this to be true. It would be weird but legal if both are of form, say, "class C implements Comparable".

The antisymmetric property prevents this from being legal.

"""The implementor must ensure sgn(x.compareTo(y)) == -sgn(y.compareTo(x)) for all x and y. (This implies that x.compareTo(y) must throw an exception iff y.compareTo(x) throws an exception.)"""

Which means that you cannot compare them to each other.

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