How to use the unsigned Integer in Java 8 and Java 9?

Question

In the Oracle "Primitive data types" page, it mentions that Java 8 adds support for unsigned ints and longs:

int: By default, the int data type is a 32-bit signed two's complement integer, which has a minimum value of −2³¹ and a maximum value of 2³¹−1. In Java SE 8 and later, you can use the int data type to represent an unsigned 32-bit integer, which has a minimum value of 0 and a maximum value of 2³²−1. Use the Integer class to use int data type as an unsigned integer. See the section The Number Classes for more information. Static methods like compareUnsigned, divideUnsigned etc have been added to the Integer class to support the arithmetic operations for unsigned integers.

long: The long data type is a 64-bit two's complement integer. The signed long has a minimum value of −2⁶³ and a maximum value of 2⁶³−1. In Java SE 8 and later, you can use the long data type to represent an unsigned 64-bit long, which has a minimum value of 0 and a maximum value of 2⁶⁴−1. Use this data type when you need a range of values wider than those provided by int. The Long class also contains methods like compareUnsigned, divideUnsigned etc to support arithmetic operations for unsigned long.

However, I find no way to declare an unsigned long or integer. The following code, for example, gives a compiler error message of "the literal is out of range" (I'm using Java 8, of course), when it should be in range (the value assigned is precisely 2⁶⁴−1):

public class Foo {
    static long values = 18446744073709551615L;
    
    public static void main(String[] args){
        System.out.println(values);
    }  
}

So, is there any way to declare an unsigned int or long?

There is no unsigned integer or unsigned long type. If you use one of the new methods, that method will treat a 32-bit or 64-bit integer as though it were unsigned. But that's all. The variable's type will still be signed, and it's up to you to remember that you're using it as an unsigned number. They didn't add unsigned literals, but maybe they'll add them to Java 9 if enough people bug them. :) — ajb
– ajb, Commented Aug 28, 2014 at 19:00
They didn't really change anything, other than adding the new methods. — Hot Licks
– Hot Licks, Commented Aug 28, 2014 at 19:08
As far as I can tell, all they did was add methods that can return unsigned values, but don't allow you to declare unsigned values. Kind of silly if you ask me, and a real pain. I wonder if one way would be to use the Integer.divideUnsigned, with one parameter being 1, the other being whatever number you want treated as unsigned. Would work as far as I can tell, but seems to be really silly way of doing things. — cluemein
– cluemein, Commented Jan 26, 2016 at 18:17
@ajb how can I be of any assistance in the "bugging" process to finally see proper unsigned in Java? :) — Matthieu
– Matthieu, Commented Mar 4, 2019 at 20:57

Nathan Hughes · Accepted Answer · 2015-04-08 15:19:03Z

95

Well, even in Java 8, long and int are still signed, only some methods treat them as if they were unsigned. If you want to write unsigned long literal like that, you can do

static long values = Long.parseUnsignedLong("18446744073709551615");

public static void main(String[] args) {
    System.out.println(values); // -1
    System.out.println(Long.toUnsignedString(values)); // 18446744073709551615
}

edited Apr 8, 2015 at 15:19

Nathan Hughes

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answered Aug 28, 2014 at 19:11

kajacx

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2 Comments

David Smiley Over a year ago

An observation I see with this is that the ordering is corrupted. If I were to get an unsigned long from some system (Twitter provides such IDs, by the way) and wanted to sort them, perhaps because I knew them to be chronological, then everything beyond Long.MAX_VALUE will actually show up before 0 as negative with Java's implementation :-(. Instead it appears one must also shift it down such that unsigned 0 maps to signed Long.MIN_VALUE.

kajacx Over a year ago

@DavidSmiley Good point. To sort unsigned longs, use Long.compareUnsigned, or pass that method as a comparator to sort functions,

Sbodd · Accepted Answer · 2017-05-16 18:16:17Z

56

Per the documentation you posted, and this blog post - there's no difference when declaring the primitive between an unsigned int/long and a signed one. The "new support" is the addition of the static methods in the Integer and Long classes, e.g. Integer.divideUnsigned. If you're not using those methods, your "unsigned" long above 2^63-1 is just a plain old long with a negative value.

From a quick skim, it doesn't look like there's a way to declare integer constants in the range outside of +/- 2^31-1, or +/- 2^63-1 for longs. You would have to manually compute the negative value corresponding to your out-of-range positive value.

edited May 16, 2017 at 18:16

answered Aug 28, 2014 at 19:05

Sbodd

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Comments

blueberry0xff · Accepted Answer · 2015-09-29 12:11:25Z

27

    // Java 8
    int vInt = Integer.parseUnsignedInt("4294967295");
    System.out.println(vInt); // -1
    String sInt = Integer.toUnsignedString(vInt);
    System.out.println(sInt); // 4294967295

    long vLong = Long.parseUnsignedLong("18446744073709551615");
    System.out.println(vLong); // -1
    String sLong = Long.toUnsignedString(vLong);
    System.out.println(sLong); // 18446744073709551615

    // Guava 18.0
    int vIntGu = UnsignedInts.parseUnsignedInt(UnsignedInteger.MAX_VALUE.toString());
    System.out.println(vIntGu); // -1
    String sIntGu = UnsignedInts.toString(vIntGu);
    System.out.println(sIntGu); // 4294967295

    long vLongGu = UnsignedLongs.parseUnsignedLong("18446744073709551615");
    System.out.println(vLongGu); // -1
    String sLongGu = UnsignedLongs.toString(vLongGu);
    System.out.println(sLongGu); // 18446744073709551615

    /**
     Integer - Max range
     Signed: From −2,147,483,648 to 2,147,483,647, from −(2^31) to 2^31 – 1
     Unsigned: From 0 to 4,294,967,295 which equals 2^32 − 1

     Long - Max range
     Signed: From −9,223,372,036,854,775,808 to 9,223,372,036,854,775,807, from −(2^63) to 2^63 − 1
     Unsigned: From 0 to 18,446,744,073,709,551,615 which equals 2^64 – 1
     */

edited Sep 29, 2015 at 12:11

answered Sep 29, 2015 at 7:09

blueberry0xff

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1 Comment

cluemein Over a year ago

Should add some explanation, not just throw code out there.

1ac0 · Accepted Answer · 2017-08-31 09:25:22Z

22

There is no way how to declare an unsigned long or int in Java 8 or Java 9. But some methods treat them as if they were unsigned, for example:

static long values = Long.parseUnsignedLong("123456789012345678");

but this is not declaration of the variable.

edited Aug 31, 2017 at 9:25

answered Aug 28, 2014 at 19:11

1ac0

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7 Comments

EKanadily Over a year ago

i wounder why not. they could have easily added uint and ulong types

1ac0 Over a year ago

@docesam in this and this docu is detailed explanation. in short, just a methods for unsigned manipulation to Integer class has been added. and if they could have easily added i don't know why they won't do it ;-)

Nayuki Over a year ago

@docesam No, they could not have "easily added uint and ulong types". That would require overhauling the JLS, JVM spec, JNI, a lot of libraries (like java.util.Arrays), reflection, and so so much more.

Nayuki Over a year ago

@Michaelangel007 Hey there, I think we're approaching this topic with different background assumptions. Care to shoot me an email and we'll talk about the details?

Michaelangel007 Over a year ago

@Nayuki Do you actually understand the difference between signed shift right vs unsigned shift right?? Hint: One sign extends, the other zero extends. Cluttering up the code and masks (i.e. & 0x7FFFFFFF) is just that -- unnecessary clutter because pre Java 8 the language was brain dead.

|

Lukas Eder · Accepted Answer · 2017-12-15 10:24:06Z

5

If using a third party library is an option, there is jOOU (a spin off library from jOOQ), which offers wrapper types for unsigned integer numbers in Java. That's not exactly the same thing as having primitive type (and thus byte code) support for unsigned types, but perhaps it's still good enough for your use-case.

import static org.joou.Unsigned.*;

// and then...
UByte    b = ubyte(1);
UShort   s = ushort(1);
UInteger i = uint(1);
ULong    l = ulong(1);

All of these types extend java.lang.Number and can be converted into higher-order primitive types and BigInteger.

(Disclaimer: I work for the company behind these libraries)

answered Dec 15, 2017 at 10:24

Lukas Eder

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