Question from Khalidmughal for >>> operator

[K2Joshi]

Hi All,
I have the following example can some guru explain me why am i getting this answer.
public class Myclass
{
public static void main ( String [ ] args )
{
test ( 1 << 32, "1 << 32" );
test ( 1 << 31, "1 << 31" );
test ( 1 << 30, "1 << 30" );
test ( 1, "1" );
test ( 0, "0" );
test ( -1, "-1" );
}
public static void test ( int i, String exp )
{
if (( i >> 1 ) != ( i >>> 1 ))
System.out.println ( exp );
}
}

select all valid answers.
a) "1<<32" b) "1<<31" C) "1<<30" d) "1" e) "0" f) "-1"
the answer is b & f.
i would really appreciate if someone can explain this.
Thanks in advance
Ketu

[William Brogden]

One key point is how x << 32 is evaluated.
For int shifts, the JVM masks off the low 5 bits,which means that no shift outside the range 0 to 31 can ever be done.
x << 32 is the same as x << 0 for x an int.
Bill

[K2Joshi]

Hi Bill,
Thanks for the explaination but can you explain me in detail.
like what about i >> 30. My problem is, i am not understanding how this is evolving.
Thanks for your time.
Ketu

[Anonymous]

Originally posted by K2Joshi:
Hi All,
I have the following example can some guru explain me why am i getting this answer.
public class Myclass
{
public static void main ( String [ ] args )
{
test ( 1 << 32, "1 << 32" );<br /> test ( 1 << 31, "1 << 31" );<br /> test ( 1 << 30, "1 << 30" );<br /> test ( 1, "1" ); <br /> test ( 0, "0" );<br /> test ( -1, "-1" );<br /> }<br /> public static void test ( int i, String exp )<br /> { <br /> if (( i >> 1 ) != ( i >>> 1 )) <br /> System.out.println ( exp );<br /> } <br /> } <br /> <br /> select all valid answers.<br /> a) "1<<32" b) "1<<31" C) "1<<30" d) "1" e) "0" f) "-1"<br /> the answer is b & f. <br /> i would really appreciate if someone can explain this.<br /> Thanks in advance<br /> Ketu

<br /> Hi ketu,<br /> look at " if (( i >> 1 ) != ( i >>> 1 )) ".When it will be satisfied? only when the "i" is negative.Now search howmany of the the above mentioned test calls result in -ve.<br /> <br /> 1) test ( 1 << 32, "1 << 32" ); <br /> // shifts 0 times.so i is +ve.<br /> i = 0000 0000 0000 0000 0000 0000 0000 0001 <br /> i >> 1 = 0000 0000 0000 0000 0000 0000 0000 0000 <br /> i >>> 1 = 0000 0000 0000 0000 0000 0000 0000 0000 <br /> <br /> 2) test ( 1 << 31, "1 << 31" ); <br /> // i here is -ve.<br /> i = 1000 0000 0000 0000 0000 0000 0000 0000 <br /> i >> 1 = 1100 0000 0000 0000 0000 0000 0000 0000 <br /> i >>> 1= 0100 0000 0000 0000 0000 0000 0000 0000<br /> <br /> 3) test ( 1 << 30, "1 << 30" );<br /> i = 0100 0000 0000 0000 0000 0000 0000 0000 <br /> i >> 1 = 0010 0000 0000 0000 0000 0000 0000 0000 <br /> i >>> 1= 0010 0000 0000 0000 0000 0000 0000 0000<br /> <br /> 4) test ( 1, "1" ); <br /> i = 0000 0000 0000 0000 0000 0000 0000 0001<br /> i >> 1 = 0000 0000 0000 0000 0000 0000 0000 0000 <br /> i >>> 1 = 0000 0000 0000 0000 0000 0000 0000 0000

5) test ( 0, "0" );
// i = 0000 0000 0000 0000 0000 0000 0000 0000

6) test ( -1, "-1" );
// i = 1111 1111 1111 1111 1111 1111 1111 1111

Hence the obvious answers for the question are: b & f( hgere only i becomes -ve and satisfies if condition.

[K2Joshi]

Thanks a billion jay,
I would have never understand without anyones help, thanks for taking your time.
Ketu