This is from an interview with Gosling and others, about simplicity:
Gosling: For me as a language designer, which I don't really count myself as these days, what "simple" really ended up meaning was could I expect J. Random Developer to hold the spec in his head. That definition says that, for instance, Java isn't -- and in fact a lot of these languages end up with a lot of corner cases, things that nobody really understands. Quiz any C developer about unsigned, and pretty soon you discover that almost no C developers actually understand what goes on with unsigned, what unsigned arithmetic is. Things like that made C complex. The language part of Java is, I think, pretty simple. The libraries you have to look up.
Java doesn't actually have unsigned primitives.
The value 127 is actually represented by '01111111' the first bit being the sign (0 is positive).
An unsigned byte would be able to hold values 0 to 255, but 127 is the maximum for a signed byte. Since a byte has 8 bits, and the signed one consumes one to hold the sign.
So if you want to represent values larger than 127 you need to use a bigger type that has a greater number of bits. The greater type also has a reserved bit for sign, but it has at least 8 bits used for the actual values, so you can represent the value 255.
That being said, you should probably avoid using byte and short because there are issues with them. You'll notice i cast the result to short, since the operators actually return int. You should just stick to int and long in java since they are implemented better.
Edit: the AND operator makes it unsigned since the sign bit is the first bit of the short, and you copy the 8 bits holding the value of the byte to the last 8 bits of the short. So if you have a negative number the first bit which is 1 (that means it's negative) actually becomes part of the value. And the short will always be positive since its sign bit is at two high of a power of two to be affected by the short.
byte: 10101101
||||||| <- actual value
short: 0000000010101101
||||||||||||||| <- actual value
Edit 2: Take note though that since the negative values use two's complement representation the value might not be what you expect it. all the positive values remain the same.
But -128 = 0x10000000 will become 128
-127 = 0x10000001 will become 129
and so on until -1 = 0x11111111 which will become 255
Best Answer
Java does not have a datatype for unsigned integers.
You can define a
long
instead of anint
if you need to store large values.You can also use a signed integer as if it were unsigned. The benefit of two's complement representation is that most operations (such as addition, subtraction, multiplication, and left shift) are identical on a binary level for signed and unsigned integers. A few operations (division, right shift, comparison, and casting), however, are different. As of Java SE 8, new methods in the
Integer
class allow you to fully use theint
data type to perform unsigned arithmetic:Note that
int
variables are still signed when declared but unsigned arithmetic is now possible by using those methods in theInteger
class.