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On 05/18/2010 06:41 PM, Roedy Green wrote:
> Here is the code for SpinnerNumberModel.setValue
>
> public void setValue(Object value) {
> if ((value == null) || !(value instanceof Number)) {

It's interesting that they use a redundant check in that condition.

http://java.sun.com/docs/books/jls/t...s.html#15.20.2

I believe I detect an error in the JLS in that section. They refer to the
type of the left-hand operand of the 'instanceof' operator as a
/RelationalExpression/, which it is not. At least not as I read the document.
The text explains what they mean there, so the rules are clear though the
syntax diagram not be.

--
Lew

In article <hsv7o1$ah4$>, Lew <>
wrote:

> On 05/18/2010 06:41 PM, Roedy Green wrote:
> > Here is the code for SpinnerNumberModel.setValue
> >
> > public void setValue(Object value) {
> > if ((value == null) || !(value instanceof Number)) {
>
> It's interesting that they use a redundant check in that condition.
>
> http://java.sun.com/docs/books/jls/t...s.html#15.20.2
>
> I believe I detect an error in the JLS in that section. They refer
> to the type of the left-hand operand of the 'instanceof' operator as
> a /RelationalExpression/, which it is not. At least not as I read
> the document.

I'm puzzled. It looks like RelationalExpression in

RelationalExpression instanceof ReferenceType

refers back through ShiftExpression, AdditiveExpression,
MultiplicativeExpression, and UnaryExpression to CastExpression
via UnaryExpressionNotPlusMinus. For example,

Object i = 1;
if ((Comparable)i instanceof Number) ...

http://java.sun.com/docs/books/jls/t...ons.html#15.16

> The text explains what they mean there, so the rules are clear though
> the syntax diagram not be.

--
John B. Matthews
trashgod at gmail dot com
<http://sites.google.com/site/drjohnbmatthews>