Signed and unsigned data types in java

Question

I have a bit of confusion regarding which unsigned data types does Java support?

I have read Why doesn't Java support unsigned ints? but I don't understand its very complicated explanation (to me at least).

Is there kind of unsigned float/double/short.Are they supported — ReflectionHack, Jan 13 '14 at 10:58
Technically, `char` is an unsigned 2-byte integer, but don't use it as one. Other than that, everything is signed. — user2357112, Jan 13 '14 at 10:59
No, there is nothing unsigned in Java. (`char` is kind of but it is not numeric) — zapl, Jan 13 '14 at 11:00
@zapl `char` is a numeric Java type. It supports all arithmetic operations. — Marko Topolnik, Jan 13 '14 at 11:01
@zapl try `char ch = '0'; ch *= 1.1; System.out.println(ch);` gives you `4` — Peter Lawrey, Jan 13 '14 at 11:02
@MarkoTopolnik @PeterLawrey Aren't those operations carried out by casting to `int` (or whatever is appropriate) so that actual math is never done on `char`? — zapl, Jan 13 '14 at 11:04
@zapl Quoting the [authoritative source](http://docs.oracle.com/javase/specs/jls/se7/html/jls-4.html#jls-4.2): `The numeric types are the integral types and the floating-point types. The integral types are byte, short, int, and long, whose values are 8-bit, 16-bit, 32-bit and 64-bit signed two's-complement integers, respectively, and char, whose values are 16-bit unsigned integers representing UTF-16 code units.` — Marko Topolnik, Jan 13 '14 at 11:07
@zapl yes, the same as `byte` and `short`, but fundamentally it is a 16-bit value which is really a number. — Peter Lawrey, Jan 13 '14 at 11:08
`if ((char)-1 > (char)1) System.out.println("Ok, you win");` — zapl, Jan 13 '14 at 11:22

Peter Lawrey · Accepted Answer · 2014-01-13T11:11:44.357

Java only supports signed types (except char) because it was assumed that one type was simpler for beginners to understand than having two types for each size. In C it was perceived to be a source of error so support for unsigned types was not included.

So the designers picked four sizes

byte, 8 bit
short, 16 bit
int, 32 bit
long, 64 bit.

and to keep things consistent they were all signed just like float and double However a signed byte is rarely very useful and given they allowed unsigned 16-bit char having an unsigned byte might have made more sense.

Where this doesn't work so well is when you have to interact with systems which use unsigned integer types. This can be source of confusion and to which type to use instead because often it doesn't make any difference. Java 8 will have operations to support unsigned types as well. These are added to the wrapper classes like Integer and Long

Evgeniy Dorofeev · Answer 2 · 2014-01-13T11:11:05.227

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All Java numeric types are signed. This was the designers decision. Some people think it was a bad idea to have signed byte. J.Bloch in an interview said "I'm going to say that the strangest thing about the Java platform is that the byte type is signed." http://www.theserverside.com/news/thread.tss?thread_id=51624

edited Jan 13 '14 at 11:11

answered Jan 13 '14 at 11:00

Evgeniy Dorofeev

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`char` is unsigned. And byte should have been unsigned IMHO for the same reason. e.g. InputStream.read() reads an unsigned byte. – Peter Lawrey Jan 13 '14 at 11:01
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Joshua Bloch would say it is strange, but in C/C++ most implementations have a signed 8-bit `char` – Nayuki Jul 30 '16 at 18:22

Signed and unsigned data types in java

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