posted 17 years ago
This program prints 1 << 31
-1
The range of int primitive is -2^31 to (2^31) - 1.
and so (1 << 31) does not fit in an int and results in a negative number.
where as due to the masking of bits,
when the value to be shifted is an int,
for the shift values of >=32, the actual size of the shift is the value of the right-hand operand masked by 31.
ie.the shift distance is always between 0 and 31.
if shift value is > 32 shift is value%32
So here, 1 << 32 = 1.
Ex:
16 << 35 => 16 << (35 % 32) => 16 << 3 = 128
16 << 32 => 16 << (32 % 32) => 16 << 0 = 16
16 >> 35 => 16 >> (35 % 32) = 2
16 >> 32 => 16 >> (32 % 32) = 16
similarly for longs
for the shift values of >=64, the actual size of the shift is the value of the right-hand operand masked by 63.
ie.the shift distance is always between 0 and 63.
if shift value is >= 64 shift is value%64
And this question tests one more concept,
in unsigned right shift operation,
if the left-hand operand is negative, the result is equivalent to the left-hand operand right-shifted by the number indicated by the right-hand operand plus two left-shifted by the inverted value of the right-hand operand.
So here -1 >>> 1 = (-1 >> 1) + (2 << ~1) = 2147483647.
and since -1 >> 1 = -1 they both are not equal.
Ex: -16 >>> 2 = (-16 >> 2 ) + ( 2 << ~2 )
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Swapna.