Can someone please explain this problem?

[Amit Parnerkar]

Can someone please explain me how can we get output 122.
This example is from Marcus Green exam.

public class TimDig{
    public static void main(String argv[]){
TimDig td = new TimDig();
td.samcov();
    }
    public void samcov(){
int i=1;
int j=2;
if((i==20) &&  (j==(i=i*2))){
}
System.out.print(i); // 1
if((i==20) & (j==(i=i*2))){}
System.out.print(i); // 2
int x = i & 2;
System.out.print(x); // 3
    }
}

According to me in both if blocks the second condition won't get executed because the first condition is false. So at line 1, i=1, at line 2 also, i=1 and at line 3 x is 0, how can the output be 122??
(code taggs added)
[ May 09, 2004: Message edited by: Barry Gaunt ]

[Anil Hulikal]

Two things:
1. First "if" uses the conditional/logical "&&", and it is short cut. So, the right hand side of the && wont get evaluated. That is why the value of i remains 1.
2. The second if statement has one "&", which is a bitwise "AND" operator, hence evaluates both operands there by assigning a new value for the variable i (i = i * 2 = 2).
As for x is concerned, it is simply a bitwise AND (0010 AND 0010).
Regards,
Anil

[Barry Gaunt]

Anil said:

2. The second if statement has one "&", which is a bitwise "AND" operator, hence evaluates both operands there by assigning a new value for the variable i (i = i * 2 = 2).
As for x is concerned, it is simply a bitwise AND (0010 AND 0010).

Unfortuately this is not the correct explanation Anil.
"&" is indeed a bitwise operation, but it is also a logical operation. Unlike "&&" both operands of "&" have to be evaluated to get its result.
The if condition:

(i==20) & (j==(i=i*2))
 

is boolean & boolean, and in this case is false & false.
In the second usage (the evaluation of x's value) it is being used as a bitwise operator, as you correctly said.

[Anil Hulikal]

Thanks, Barry. Sorry, I did not mean to mislead. I was simply trying to explain in the context of how the value of variable "i" was getting assigned with a new value. I agree that I did not fully explain about "&".

[Barry Gaunt]

No problem, Anil. (I've made more mistakes than most on these forum I bet )

[Amit Parnerkar]

Thanks Anil and Barry, I think I was confused with single "&". This explanation really helps
Thank you
Amit