Java简短加法问题 [英] Java Short addition questions

问题描述

这可能已经在另一篇文章中得到了回答，但是我只是不明白为什么我的测试Java应用程序(1.7.0_01)无法编译某些内容.

This may have already been answered in another post, but I just am not getting why something won't compile in my test Java app (1.7.0_01).

它将编译:

Short a = (short)17;
a = (short)2 + 1;

我知道"a + a"将产生一个整数.这样编译就可以了:

I know that "a + a" will result in an integer. This compiles fine:

Short a = (short)17;
int shortTest = a + a;

那为什么不编译呢?

Short a = (short)17;
a = (short)a + a;

此外，我是否可以假设由于转换为整数而不能在短裤上使用+ =，-=等...?如果可以进行这些操作，有人可以提供示例吗?

Also, am I right to assume you can't use +=, -=, etc... on Shorts because of the conversion to integer? If it's possible to do those operations, can someone provide an example?

编辑1
由于有人建议将它复制为原始类型'简短"-用Java进行转换.但是，我的示例围绕Wrapper的"Short"对象展开.围绕包装Wrapper对象有重要且更复杂的规则，这是我认为需要重点关注的规则.

Edit 1
There's been some votes to close this post as it's been suggested that it's a duplicate of Primitive type 'short' - casting in Java. However, my example revolves around the Wrapper "Short" object. There are important and more complicated rules around casting Wrapper objects and that's what I think needs to be focussed on.

而且，正如我的原始文章所指出的那样，我正在寻找第三个代码块后面的为什么" .我也想知道在短包装纸上是否可以使用"+ ="，-="等.

Also, as my original post indicates, I'm looking for the "why" behind the 3rd code block. I'm also interested to know if it's possible to use "+=", "-=", etc... on the Short Wrapper.

推荐答案

由于某些原因，似乎删除了正确答案:(short)a + a 等同于((short)a)+ a ，您正在寻找(short)(a + a).

Seems the correct answer was removed for some reason: (short) a + a is equivalent to ((short) a) + a, you're looking for (short)(a + a).

其背后的原因"是运算符优先级，> 1 + 2 * 3 是 7 ，而不是 9 .是的，基元和文字被视为相同.

The 'why' behind it is operator precedence, same reason why 1 + 2 * 3 is 7 and not 9. And yes, primitives and literals are treated the same.

你不能做 Short s = 1;s + = 1; ，因为它与 a = a + 1; 相同，其中a被转换为 int 和 int 不能转换为 Short .您可以像这样修复长版本: a =(short)(a + 1); ，但是无法通过 + = 在其中进行显式转换.

You can't do Short s = 1; s += 1; because it's the same as a = a + 1; where a is converted to an int and an int can't be cast to a Short. You can fix the long version like so: a = (short) (a + 1);, but there's no way to get the explicit cast in there with +=.

这很烦人.

这篇关于Java简短加法问题的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！