operator

[Weerawit Maneepongsawat]

pls help what the result??
public class Question48{
public static void main(String[] args) {
int i = 4*6-3/2<<2*5>>>1%2-4^3;
System.out.println(i);
}
}
why pls explain abount this i'm so scare

[Valentin Crettaz]

You won't get any questions like this in the real exam, that's why I wrote at the top of my mock exam that it is much more difficult than the real exam and that you should not take it until you feel really comfortable. I have created this mock exam for people who would like to delve a little deeper into the details of the Java language, but it is by no means required to have that level of knowledge to pass the SCJP exam.
Anyway, the question has to do with operator precedence, the whole evaluation details are provided in the answer when you click on the Submit button at the bottom of the page.
By smartly placing the paranthesis at the right spots we get the following expression
((((4*6)-(3/2))<<(2*5))>>>((1%2)-4))^3
that evaluates to 3 (answer D)
[ March 07, 2003: Message edited by: Valentin Crettaz ]

[Weerawit Maneepongsawat]

thank valentin but i confuse about operator >> , >>>, /, *
which operator must done frist

[dennis zined]

I have a similar question but not as complex.
In a shift operation, given for example:
a >> b or a << b
Can 'b' have a negative value or rather would it make any sense for it to be negative? Would such questions come out in the exam?
I've figured out the behavior of a negative b for right shift operators but couldnt understand the behavior for left shift operators.

[Valentin Crettaz]

weerawit,
please see the following operator precedence table: http://www.mindprod.com/jcheat.html (at the bottom)
dnz znd,
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[dennis zined]

Changed it. Sorry.

[Valentin Crettaz]

As far a shifting is concerned, b will always be taken modulus 32 (or 64 if a is of type long). Thus, the rules of the % (modulus) operator apply to the negative b.
Please check out the discussion Shift with -ve operand???.

[dennis zined]

Thanks Valentin.

[Weerawit Maneepongsawat]

thank valentin

[Sarma Lolla]

Arithmetic operators have high precedence followed by shift and last bitwise.
So in this case
int ii = 4*6-3/2<<2*5>>>1%2-4^3;
ii = 24-1<<10>>>1-4^3;
ii = 23<<10>>>(-3)^3;
ii = 23<<10>>>29^3;
ii = 0^3;
ii = 3;
The only thing is when the second operand for shift is -ve then convert the negative number to bits and take the lower 5 bits if the first operand is int or take 6 lower bits if the first operator is long. Other wise just add 32 to the number(in this case 32 -3 =29.)
Thats it...