blocks|key|1244455|text|编译器警告你，因为byte%2Bbyte+=+int因此，它警告你何时尝试添加两个字节(本质上是加法后的整数)并将其分配给一个字节，这将导致精度损失，因为字节只能容纳8位，而作为整数可以容纳32位。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1244456|但是，当您使用时，这不会给您一个警告。|1244457|++++a%2B=b;+//|code-block|syntax|javascript|1244458|entityMap^0|9|F|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|R|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|S|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

Compiler warns you because <code>byte+byte = int</code> Thus, it warns you when to try to add two bytes(essentially an int after the addition) and assign it to an byte, which would lead to loss of precision, as byte can only hold 8 bits where as an int can hold 32 bits.

However, this would not give you a warning when you use <a href="http://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.26.2" rel="nofollow">compound assignment operator</a>. 

<pre><code> a+=b; //
</code></pre>

blocks|key|836152|text|add操作导致byte变量被提升为int。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|836153|请参阅此问题的答案Add+bytes+with+type+casting,+Java|offset|length|836154|我不太明白为什么使用c#，但似乎是为了c#(是的，java也有类似的结果)，这是为了性能。有关详细信息，请参阅此处byte+%2B+byte+=+int...+why?|836155|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/9815970/add-bytes-with-type-casting-java|1|https://stackoverflow.com/questions/941584/byte-byte-int-why^0|0|9|X|0|0|1L|P|1|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|S|8|@]|9|@$D|T|E|U|1|V]]|A|$]]|$1|F|3|G|5|6|7|W|8|@]|9|@$D|X|E|Y|1|Z]]|A|$]]|$1|H|3|-4|5|6|7|10|8|@]|9|@]|A|$]]]|I|$J|$5|K|L|M|A|$N|O]]|P|$5|K|L|M|A|$N|Q]]]]

the add operations cause the byte variable to be promoted to int.

see the answer to this question <a href="https://stackoverflow.com/questions/9815970/add-bytes-with-type-casting-java">Add bytes with type casting, Java</a>

i dont quite know why with java, but it seems for c#(yes, c# have similar result), it's for performance sake. See here for details <a href="https://stackoverflow.com/questions/941584/byte-byte-int-why">byte + byte = int... why?</a>

blocks|key|2960246|text|它会警告您的|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2960247|2960248|可能的精度损失|blockquote|2960249|2960250|2960251|因为加法运算符使每个byte值在加法完成之前被提升为int+(二进制数值提升)。因此，byte%2Bbyte将是一个int结果，要将其分配回字节a，它需要将int向下转换为byte。如果加法的值大于可以存储为byte值的值，则向下转换可能导致精度损失。|offset|length|style|CODE|2960252|您可以通过显式向下转换为a=(byte)(a%2Bb)来强制编译器接受这一点，因为您知道风险，而编译器不应该关心这些信号。|2960253|entityMap^0|0|0|0|0|0|A|4|Q|3|1K|3|1Y|1|24|3|2C|4|2U|4|0|C|D|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|S|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|T|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|U|8|@]|9|@]|A|$]]|$1|G|3|-4|5|6|7|V|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|W|8|@$J|X|K|Y|L|M]|$J|Z|K|10|L|M]|$J|11|K|12|L|M]|$J|13|K|14|L|M]|$J|15|K|16|L|M]|$J|17|K|18|L|M]|$J|19|K|1A|L|M]]|9|@]|A|$]]|$1|N|3|O|5|6|7|1B|8|@$J|1C|K|1D|L|M]]|9|@]|A|$]]|$1|P|3|-4|5|6|7|1E|8|@]|9|@]|A|$]]]|Q|$]]

It warns your 

<blockquote>
 possible loss of precision
</blockquote>

because the addition operator causes each of the <code>byte</code> values to be promoted to an <code>int</code> before the addition is done (Binary Numeric Promotion). So byte+byte would be an <code>int</code> result and to assign back to a byte <code>a</code> it needs to downcast <code>int</code> to <code>byte</code>. The downcast may result in loss of precision if the value of the addition is greater than can be stored as a <code>byte</code> value.

You can force compiler to accept this by explicitly downcast as <code>a=(byte)(a+b)</code> where signals that you know the risk and compiler shouldn't care.

While learning about implicit and explicit type casting, I tried the following code:

<pre><code>class Implicit
{
 public static void main(String args[])
 {
 byte a=10;
 byte b=20;

 a=a+b; //

 System.out.println(a);
 }
}
</code></pre>

The compiler reports:

<img src="https://i.stack.imgur.com/LNHtO.png" alt="enter image description here"> 

I tried this code to see if a unary operator or any other operation in such example can cause the data type on the Right Hand Side to change.

Is this what is happening here? If so, what is the reason? What other situations would cause the data type to be altered?

Java (Implicit type casting): Does a unary operator affect the data type of the variables in operation?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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在学习隐式和显式类型转换的同时，我尝试了以下代码：class Implicit{    public static void main(String args[])    {        byte a=10;        byte b=20;        a=a+b; //        System.out.p...

问Java (隐式类型转换)：一元运算符是否会影响操作中变量的数据类型？
EN

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问Java (隐式类型转换)：一元运算符是否会影响操作中变量的数据类型？EN