Java left shift and zero padding
I want to do a left shift, but filling in zero, just like
int number = 20 >>> 10 = ( 0000 0000 0000 0000 0000 0000 0001 0100 )
int number = 20 >>> 32 = ( 0000 0000 0000 0000 0000 0000 0000 0000 )
I want to do the same with left shift since there is no <<<operator for left shift
int number = 20 << 32 = 0000 0000 0000 0000 0000 0000 0001 0100 ;
I want to fill it with zeros just like the →> operator. So how can I do this?
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The shift operator <<
will cast zeros the way you want.
The reason there are two right shift operators ( >>
and >>>
) is because in 2's complement form, negative numbers have a bit value 1
at the leftmost position. The right shift operator >>
will add the sign bit ( 1
in the case of negative numbers and 0
in the case of positive numbers or zero) on the left side, while the other ( >>>
) will always add zeros.
Both right shift operators use.
The language specification states that if the bit shift operators are applied to int
, since it is a 32-bit length, only the least significant 5 bits are used to determine how many times to shift a number.
So, if you shift by 32, which is 100000
in binary, it is equivalent to shifting by 0, which means no shift! And if you want to shift 64-bit long
, the least significant bit is only used to indicate how many times to shift.
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You need to use the long type and only use the least significant 32 bits. Use and operator for this.
long intMask = 0x00000000FFFFFFFFL;
long x = 0x00000000FFFFFFFFL;
x = x<<32;
int xi = (int)(x & intMask);
System.out.println("xi=" + xi); //Result will be 0
See question: Declaring an unsigned int in Java
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