为什么我可以将字符添加到字符串但不能将字符添加到字符?
所以我想将一个字符添加到一个字符串中，并且在某些情况下想要将该字符加倍然后将其添加到一个字符串中(即先添加到它本身).我试过了，如下所示.
So I wanted to add a character to a string, and in some cases wanted to double that characters then add it to a string (i.e. add to it itself first). I tried this as shown below.
char s = 'X';
String string = s + s;
这引发了一个错误，但我已经在字符串中添加了一个字符，所以我尝试了:
This threw up an error, but I'd already added a single character to a string so I tried:
String string = "" + s + s;
哪个有效.为什么在总和中包含一个字符串会导致它起作用?是否添加了一个字符串属性，由于字符串的存在，该属性只能由字符转换为字符串时使用?
Which worked. Why does the inclusion of a string in the summation cause it to work? Is adding a string property which can only be used by characters when they're converted to strings due to the presence of a string?
推荐答案
因为String + Char = String，类似于int + double = double.
It's because String + Char = String, similar to how an int + double = double.
尽管其他答案告诉你什么，Char + Char 是 int.
Char + Char is int despite what the other answers tell you.
字符串 s = 1;//由于类型不匹配导致的编译错误.
String s = 1; // compilation error due to mismatched types.
您的工作代码是 (String+Char)+Char.如果你这样做了: String+(Char+Char) 你会在你的字符串中得到一个数字.示例:
Your working code is (String+Char)+Char. If you had done this: String+(Char+Char) you would get a number in your string. Example:
System.out.println("" + ('x' + 'x')); // prints 240
System.out.println(("" + 'x') + 'x'); // prints xx - this is the same as leaving out the ( ).
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