What's the difference between the ">>" and ">>>" operators?
Unsigned shifting, on the other hand, ignores the sign of the number, and unsigned right shifting a negative number will result in a positive number -- which is why you generally shouldn't use the unsigned shift unless you are considering your number as unsigned.
The reason for the difference is that bytes, shorts, ints, and longs are all stored in two's-complement form (i.e. as signed numbers). This means, among other things, that the most significant bit is the sign bit, so that if the sign bit is 0 the number is positive, and if the sign bit is 1 the number is negative. If you want to divide a signed number by two by shifting it right, you have to retain the sign bit.
If you are treating a number as unsigned, then you should use the unsigned shift operator. Otherwise you should use the signed shift operator, which retains the sign bit.