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# Double wrapper class doubt?

Ranch Hand
Posts: 10192
3
Hi guys,

The code below is also from Dan Chisholm,

Help me out guys with the commented line above?

Ranch Hand
Posts: 7729
I'll start you off:

Looking at the API for Double, I see that isNaN returns a boolean. So on the lefthand side of == must be a boolean. It can only be the result of v != v.

So we have:

Now you look at the Double API to see what the result of v != v is (where v is NaN). It's in the description of Double.NaN.

Joe Harry
Ranch Hand
Posts: 10192
3
Barry,

I knew that NaN is not equal to anything and when we say NaN == NaN returns false and NaN != anything will return true. My confusion was on how to group the operators like you showed by placing braces...

(v != v) == Double.isNaN(v)...

But still I want to know based on what rules we group the operators??

Thanks for the help.

Ranch Hand
Posts: 88

Originally posted by Jothi Shankar Kumar Sankararaj:
Barry,

I knew that NaN is not equal to anything and when we say NaN == NaN returns false and NaN != anything will return true. My confusion was on how to group the operators like you showed by placing braces...

(v != v) == Double.isNaN(v)...

But still I want to know based on what rules we group the operators??

Thanks for the help.

== and != operators have equal precedence. And for equal precedenct operators execution happens from left to right.

Joe Harry
Ranch Hand
Posts: 10192
3
Thanks for the help. So concluding, when there are two or more equal precedence operators in a statement, then the execution happens from left to right.

Thanks guys.

Ranch Hand
Posts: 381

Satish Kota writes..
== and != operators have equal precedence. And for equal precedenct operators execution happens from left to right.

Jothi,Is this question is from mock for 1.4?Because I guess operator precedence is not a part of SCJP 5.0 exam.

Joe Harry
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Posts: 10192
3
Sanjeev,

I'm aiming for 1.4 version. So the question is for 1.4 exam.

Barry Gaunt
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Posts: 7729
Jothi, this is all very basic stuff. I get the impression you are not referring to any basic Java book where these topics are explained rather early on. Are you not, in fact, reading an introductory book on Java? (I do not refer to K & B because it expects its readers to have already learnt Java).

Anyway, operator precedence and association is very well presented on Roedy Green's Java Glossary Site

Joe Harry
Ranch Hand
Posts: 10192
3
Barry,

Thanks for the help.

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