如何在Java 8和Java 9中使用unsigned Integer？ [英] How to use the unsigned Integer in Java 8 and Java 9?

问题描述

在Oracle原始数据类型页面中，它提到Java 8增加了对无符号整数和长整数的支持：

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

int ：默认情况下， int 数据类型是32位带符号的二进制补码整数，其最小值为-2 ³¹ 且最大值2 ³¹ -1。 在Java SE 8及更高版本中，您可以使用 int 数据类型来表示无符号的32位整数，其最小值为0且最大值为2 ³² -1。使用 Integer 类来使用 int 数据类型为无符号整数。有关详细信息，请参阅数字类一节。静态方法如 compareUnsigned ， divideUnsigned 等已添加到整数 class支持无符号整数的算术运算。

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 ： long 数据类型是64位二进制补码整数。签名的 long 的最小值为-2 ⁶³ ，最大值为2 ⁶³ -1。 在Java SE 8及更高版本中，您可以使用 long 数据类型来表示无符号的64位 long ，其最小值为0，最大值为2 ⁶⁴ -1。当需要比int提供的值更宽的值时，请使用此数据类型。 Long 类还包含 compareUnsigned ， divideUnsigned 等方法支持无符号 long 的算术运算。

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.

然而，我找不到办法声明无符号长整数。例如，下面的代码给出了编译器错误消息文字超出范围（我当然使用的是Java 8），当它应该在范围内时（指定的值恰好为2 ^64） -1）：

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);
    }  
}

那么，有没有办法声明一个unsigned int或者很长？

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

推荐答案

根据您发布的文档和这篇博客文章 - 在无符号int / long和签名之间声明原语时没有区别。 新支持是在Integer和Long类中添加静态方法，例如 Integer.divideUnsigned 。如果您没有使用这些方法，那么长于2 ^ 63-1的无符号只是一个带有负值的普通旧长。

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.

从快速浏览，看起来有一种方法可以在+/- 2 ^ 31-1或+/- 2 ^ 63-1之外的范围内声明整数常量。您必须手动计算与超出范围正值相对应的负值。

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.

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