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The moose likes Programmer Certification (SCJP/OCPJP) and the fly likes shift operators Big Moose Saloon
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shift operators

sanjana narayanan
Ranch Hand

Joined: Nov 25, 2003
Posts: 142
Hi,

I am not able to understand shift operators. Can someone help me..
Though i know the basics of left and right shift operators, i encounter the problem when it comes to the calculations.
Pl go thru the following code..
class BitShift {
public static void main(String [] args) {
int x = 0x80000000;
System.out.println("Before shift x equals " + x);
x = x >> 4;
System.out.println("After shift x equals " + x);
}
}
I think in the exam we are not allowed to use the calculators..So how do i know x=-2147483648 and after shift x=-134217728
-sanjana
Vad Fogel
Ranch Hand

Joined: Aug 25, 2003
Posts: 504
You're not up to doing excessively laborious calculations on the exam, just stick to what's covered in K&B, they've done an awesome job about it. All you need to understand is how the shifting works in general, when the sign changes, and when the result remains the same. Also, make sure you're familiar with shifting by negative numbers and how implicit conversion applies to the operands. In your example, what's worth knowing is that 0x80000000 represents Integer.MIN_VALUE, you're right-shifting it by 4, so the sign stays negative, and the result will be Integer.MIN_VALUE/16.
 
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