为什么Java不支持无符号整数?

在我看来,这是一个奇怪的遗漏,因为它们允许人们编写不太可能在意外的大输入上产生溢出的代码。

此外,使用无符号整数可以是一种自我文档的形式,因为它们表明无符号整型所要保存的值永远不应该是负数。

最后,在某些情况下,无符号整数对于某些运算(如除法)更有效。

包含这些的缺点是什么?


当前回答

这是对高斯林和其他人的采访,关于简单:

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.

其他回答

http://skeletoncoder.blogspot.com/2006/09/java-tutorials-why-no-unsigned.html

这个家伙说,因为C标准定义了包含无符号整型和有符号整型的操作被视为无符号整型。这可能导致负符号整数滚动到一个大的无符号整数,可能会导致错误。

这是对高斯林和其他人的采访,关于简单:

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.

作为处理过无符号算术的人,我可以向您保证,在Java中确实没有必要使用无符号数字。

以C语言为例。让我们这样写:

unsigned int num = -7;
printf("%d", num);

你能猜到上面印的是什么吗?

-7

哇!无符号整数是负的!完全正确。没有真正的正整数。无符号整数只是一个n字节(取决于C语言中的体系结构)的值,它不为符号分配MSB。它不检查分配或读取的数字的实际符号。

我知道这个帖子太老了;但是,在Java 8及以后版本中,您可以使用int数据类型来表示无符号32位整数,其最小值为0,最大值为232−1。使用Integer类使用int数据类型作为无符号整数,并且像compareUnsigned(), divideUnsigned()等静态方法已经添加到Integer类中,以支持无符号整数的算术操作。

我能想到一个不幸的副作用。在java嵌入式数据库中,使用32位id字段可以拥有的id数量是2^31,而不是2^32(~ 20亿,而不是~ 40亿)。