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what is the value of 8 | 9 & 10 ^ 11 ?

paul wheaton
Trailboss

Joined: Dec 14, 1998
Posts: 20635
    ∞

Are we really going to get a question like this? IOW-- do we really have to memorize the precedence of the bitwise operators?

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paul wheaton
Trailboss

Joined: Dec 14, 1998
Posts: 20635
    ∞

And what is the answer to this anyway? I don't have a reference handy for this kind of thing and left to right isn't giving me one of the answers provided (8, 9, 10 or 11).
Frank Carver
Sheriff

Joined: Jan 07, 1999
Posts: 6920
OK, my guess is
<pre>
8 | ((9 & 10) ^ 11)
=> 1000 | ((1001 & 1010) ^ 1011)
=> 1000 | ( 1000 ^ 1011 )
=> 1000 | 0011
=> 1011
=> 11
</pre>
Is this right?


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paul wheaton
Trailboss

Joined: Dec 14, 1998
Posts: 20635
    ∞

I have a reference book now, but it shows the bitwise operators all in the same precedence, so from that I would guess that left to right would apply....
I loaded the expression into a test program. Compile and run... The answer is 11 - you were right.
The real question is: Do we need to know this level of precedence for the SCJP2 exam?
Frank Carver
Sheriff

Joined: Jan 07, 1999
Posts: 6920
I don't know which "reference" book you have, but I use Java in a Nutshell (2ed) from O'Reilly which correctly lists the precedence of all the operators on pages 228 and 229.
And no, I don't think you really need to know it in that much detail. Especially as you can afford to lose a few points and still pass.
paul wheaton
Trailboss

Joined: Dec 14, 1998
Posts: 20635
    ∞

I'm wanting to get a high score. I'm certain I could have passed the test weeks ago. But it's those last few percentage points I want to reduce.
So - this sort of stuff WILL be on the test. Right?
I have the Java in a nutshell book - thanks for the info. I'll have to try to memorize this stuff I guess.
Anonymous
Ranch Hand

Joined: Nov 22, 2008
Posts: 18944
i post this from jls 15.21 for operator precedence for & , ^ and |.
These operators have different precedence, with & having the highest precedence and | the lowest precedence. Each of these operators is syntactically left-associative (each groups left-to-right).
[This message has been edited by rahul_mkar (edited May 04, 2000).]
Herbert Maosa
Ranch Hand

Joined: May 03, 2000
Posts: 289
My friend, you really need any point that comes your way, and you can not afford to lose apoint when you dont know what the next question brings. You DO have to know the operator precedence because it accounts to answering so many questions. Moreover, you need to know it to be a real programmer.
Nalini Mistry
Ranch Hand

Joined: Mar 21, 2000
Posts: 64
I made up a mneomonic (im sure i spelled that wrong!) for the operator precedence
"you ask bullshit then assign"
U - Unary
A - Arithmetic
S - Shift
C - (mneumonic licence) Comparison
B - Bitwise
S - Shortcut
T - Ternary
A - Assign
Works out to U ASC BullShit Then Assign
Anonymous
Ranch Hand

Joined: Nov 22, 2008
Posts: 18944
hi Nalini Mistry
could u please provide us with an example to clarify and end this thread
Eric Barnhill
Rancher

Joined: Feb 25, 2000
Posts: 233

Thanks for the mnemonic, I like it.
Eric
 
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