Shift operators

[Faqeer Khudaka]

Hi,


I found this question in one of the mock exams:

 Which of the following are correct?
 
128 >> 1 gives 64 
128 >>> 1 gives 64 
128 >> 1 gives �64 
128 >>> 1 gives �64   

Correct answer is A & B. My answer was B&C cause when 128 >> 1 is computed, the rule is that whatever the most significant bit is, that has to be "filled" from the left. In this case when 128(10000000) is shifted right by 1 bit, another 1 will be added cause initially the most significant bit of 128 was 1. This will give us 11000000 which comes out to be 192.
Am i correct??

Thanks
Faqeer

[Jan Valenta]

Don't forget that there is automatic promotion of the operands to ints. Therefore you are shifting (00000000 00000000 00000000 10000000) and the initial zero stays zero.

Jan

[ven kaar]

i think the correct answer is 64 for both

public class ClazzShift {
 
public static void main(String[] args) {
System.out.println(128>>1);
System.out.println(128>>>1);
}
 
}

http://java.sun.com/docs/books/tutorial/java/nutsandbolts/bitwise.html

considering 128 as int datatype

128 value is 00000000 00000000 00000000 10000000
based on the referred link above

>> 00000000 00000000 00000000 01000000 (fills with highest (sign) bit on the left side )
>>> 00000000 00000000 00000000 01000000 (fills with 0 bits on the left side )

[Faqeer Khudaka]

Thanks guys.
I didnt pay attention to the int promotion thing.

[Bert Bates]

remember this topic is on the 1.4 exam, but it's NOT on the 1.5 exam.