Why doesn't Java support unsigned ints?

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.

Reading between the lines, I think the logic was something like this:

• generally, the Java designers wanted to simplify the repertoire of data types available
• for everyday purposes, they felt that the most common need was for signed data types
• for implementing certain algorithms, unsigned arithmetic is sometimes needed, but the kind of programmers that would be implementing such algorithms would also have the knowledge to "work round" doing unsigned arithmetic with signed data types

Mostly, I'd say it was a reasonable decision. Possibly, I would have:

• made byte unsigned, or at least have provided a signed/unsigned alternatives, possibly with different names, for this one data type (making it signed is good for consistency, but when do you ever need a signed byte?)
• done away with 'short' (when did you last use 16-bit signed arithmetic?)

Still, with a bit of kludging, operations on unsigned values up to 32 bits aren't tooo bad, and most people don't need unsigned 64-bit division or comparison.

This is an older question and pat did briefly mention char, I just thought I should expand upon this for others who will look at this down the road. Let's take a closer look at the Java primitive types:

byte - 8-bit signed integer

short - 16-bit signed integer

int - 32-bit signed integer

long - 64-bit signed integer

char - 16-bit character (unsigned integer)

Although char does not support unsigned arithmetic, it essentially can be treated as an unsigned integer. You would have to explicitly cast arithmetic operations back into char, but it does provide you with a way to specify unsigned numbers.

char a = 0;char b = 6;a += 1;a = (char) (a * b);a = (char) (a + b);a = (char) (a - 16);b = (char) (b % 3);b = (char) (b / a);//a = -1; // Generates complier error, must be cast to charSystem.out.println(a); // Prints ? System.out.println((int) a); // Prints 65532System.out.println((short) a); // Prints -4short c = -4;System.out.println((int) c); // Prints -4, notice the difference with chara *= 2;a -= 6;a /= 3;a %= 7;a++;a--;

Yes, there isn't direct support for unsigned integers (obviously, I wouldn't have to cast most of my operations back into char if there was direct support). However, there certainly exists an unsigned primitive data type. I would liked to have seen an unsigned byte as well, but I guess doubling the memory cost and instead use char is a viable option.

Edit

With JDK8 there are new APIs for Long and Integer which provide helper methods when treating long and int values as unsigned values.

• compareUnsigned
• divideUnsigned
• parseUnsignedInt
• parseUnsignedLong
• remainderUnsigned
• toUnsignedLong
• toUnsignedString

Additionally, Guava provides a number of helper methods to do similar things for at the integer types which helps close the gap left by the lack of native support for unsigned integers.