pls help: a bit shift question

[Jenny Hua]

http://www.geocities.com/skmajji/Main.html
question #5:
The following code will print
1: int i = 1;
2: i <<= 31;<br /> 3: i >>= 31;
4: i >>= 1;
5:
6: int j = 1;
7: j >>= 31;
8: j >>= 31;
9:
10: System.out.println("i = " +i );
11: System.out.println("j = " +j);
A) i = 1
j = 1
B) i = -1
j = 1
C) i = 1
j = -1
D) i = -1
j = 0
why the answer is D? thanks in advance . I think i should be 0.

[Alex Sbityakov]

1: int i = 1; i is 1
2: i <<= 31; i is -1 (since the leftmost bit is 1)<br /> 3: i >>= 31; i is again 1
4: i >>= 1; i is -1, because the shift operation keeps
the sign of the number (as opposed to >>>)
Alex

[wei ma]

int i = 1; i = "00000000000000000000000000000001"
i<<=31; i = "10000000000000000000000000000000"<br /> i>>=31; i = "11111111111111111111111111111111"
i>>=1; i = "11111111111111111111111111111111"
so the result of i should be -1,
(2's complement of 00000000000000000000000000000001 )
wei

[Alex Sbityakov]

I made a mistake in my earlier post. Wei's absolutely right.
But the point is your confusion stems from the fact that >> operator inserts 0 or 1 as the leftmost bit depending on the sign of the operand (in this case negative, so it fills in with 1's).
Alex