operators

[shabbir zakir]

Q9. What is the output of running the following code (Select one Correct answer):
1. public class Q9{
2.
3. public static void main(String[] args){
4.
5. int i=3;
6.
7. System.out.println(i*=2 + i++);
8.
9. }
10.
11. }
Now in this sum the extended assignment has the lowest prcedence. So the right side is evaluated first So
1) 2 + 3(4)= 5
2) 4 * 5 = 20
So i becomes 20. So howcome 15. please explain

[Sivalingam Sivasuthan]

Hi shabbir zakir:
1)int i=3;
2)i*=2*i++;
3) first the Expression will be evaluated.
4) 3*=2*3(4)
5) 3*=6
6) ans will be 18.
Siva.

[Udayan Naik]

Hi Shabbir.Let's go through the code

i*=2 + i++;

1)The actual expression can be also written as

i=i*(2 + i++);

since we are using a shorthand operator.When this expression will be evaluated,the CURRENT value of i will be used.Hence the expression will be now i=3*(2+i++);
However,assignment has lower priority than the other operators used in the expression,thus the value 3 will be pushed on stack and the (2+i++) will be evaluated.
2)Now the expression (2+i++) has to be evaluated,which will come to 2+3=5,since a post-fix operator (i++) is used.Hence the expression (2+i++) evaluates to (2+3)
3)Value of i will now be incremented,because of i++.Hence now i=4.
4)Now the stored value is retrieved and it is multiplied with the result obtained in step 2) above.Thus,now the expression becomes i = 3*5, ie i=15, thus overwriting the value of i obtained in step 3) above.
I hope i have been clear enough.
------------------
Udayan Naik
Sun Certified Java 2 Programmer
[This message has been edited by Udayan Naik (edited March 01, 2001).]

[Lokesh Mahajan]

Hello Dear
the answe is right it's 15,
i*=2 + i++;
1> i= 3 ;
2> i++ this is postincrement so value of i remains 3
3> 2 + i++ = 5,
4>i*=5 (now its become 5) so its evaluted as i = i * 5 i.e.(i= 3 * 5) = 15,
so answer is 15,
if it was like this i*=2 + ++i;
than
1> i = 3;
2>++i= 4 (because its preincrement but i remains 3 only);
3> 2+4 = 6;
4>i*= 6 (so its become i = 3 * 6 )
5> 18
so in this case it will print 18,
correct me if i am wrong.
Love
Lokesh

[shabbir zakir]

Thanks a lot. Now i understand what have been forgetting.