问题描述
在此程式码片段中：
c = (char)(c - 'A' + 'a');
为什么我们需要（char） ？这是类型转换正确吗？
Why do we need the (char)? That's type casting right?
假设赋值语句右边的 c 是大写字母。我假设我们在这里进行Unicode加减法。
Assume the c on the right side of the assignment statement is a capital letter. I assume we're doing Unicode addition and subtraction here.
这是我读的Java书中的代码片段：
This is the snippet from the Java book that I'm reading:
我不明白（char） cast的点？如果我们不使用（char） cast，会有什么不同？
I don't understand the point of the (char) cast? What would be different if we didn't use the (char) cast? What is casting more generally?
推荐答案
char 是，当您执行算术时结果是 int （部分地说明数值运算符，其导致类型 int 或 long ，并添加添加运算符 + 和 - ）。
char is an integral type in Java, and when you perform arithmetic the result is an int (JLS-4.2.2. Integer Operations says, in part, the numerical operators, which result in a value of type int or long and adds that does include the additive operators + and -).
char c = 'A';
System.out.printf("'%c' = %d%n", c, (int) c);
int d = (c - 'A' + 'a'); // c - 65 + 97
System.out.printf("'%c' = %d%n", (char) d, d);
我得到
'A' = 65
'a' = 97
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