conversions

[Puja S]

Hi,

I'm finding difficulty in solving the following question.These type of questions are taking a lot of time and if they come in the exam i'll be

Please can anybody give me a simple way solve them.

class EBH019 {
public static void main (String args[]) {
int i1 = 0xffffffff, i2 = i1 << 1;
int i3 = i1 >> 1, i4 = i1 >>> 1;
System.out.print(Integer.toHexString(i2) + ",");
System.out.print(Integer.toHexString(i3) + ",");
System.out.print(Integer.toHexString(i4));
}}

What is the result of attempting to compile and run the program?

a. Prints: ffffffff,ffffffff,ffffffff
b. Prints: ffffffff,ffffffff,7fffffff
c. Prints: ffffffff,7fffffff,ffffffff
d. Prints: ffffffff,7ffffffe,7ffffffe
e. Prints: fffffffe,ffffffff,ffffffff
f. Prints: fffffffe,ffffffff,7fffffff
g. Prints: fffffffe,7fffffff,ffffffff
h. Prints: fffffffe,7fffffff,7fffffff
i. Run-time error
j. Compile-time error
k. None of the above


The answer is f.

Thanks

[marc weber]

Note that each hexadecimal digit represents 4 binary bits, since 2^4 = 16. (Similarly, each octal digit represents 3 binary bits, since 2^3 = 8.)

For example, Ox369cf is...
 
0011 0110 1001 1100 1111
3    6    9    c    f
 
So 0xffffffff is easy to work with, because 
it's all one's...
 
1111 1111 1111 1111 1111 1111 1111 1111
f    f    f    f    f    f    f    f
 
Now, if we shift this to the left by 1, we get:
 
1111 1111 1111 1111 1111 1111 1111 1110
f    f    f    f    f    f    f    e
 
And if we shift the original to the right by 1, 
we get no change, because the (signed) right 
shift fills left bits with whatever the most 
significant bit was:
 
1111 1111 1111 1111 1111 1111 1111 1111
f    f    f    f    f    f    f    f
 
But if we shift the original to the right by 1 
with an unsigned right shift, then the left 
bits are filled with zeros:
 
0111 1111 1111 1111 1111 1111 1111 1111
7    f    f    f    f    f    f    f

[ January 21, 2005: Message edited by: marc weber ]

[Puja S]

a million thanks to you marc......it is now clear to me.
It was that I was not going on the right track......but now it looks very simple......I'll try some more questions on the same.