switch语句中的最终变量大小写 [英] final variable case in switch statement

问题描述

        final int a = 1;
        final int b;
        b = 2;
        final int x = 0;

        switch (x) {
            case a:break;     // ok
            case b:break;     // compiler error: Constant expression required

        }
        /* COMPILER RESULT:
                constant expression required
                case b:break;
                     ^
                1 error
        */

为什么我会得到这种错误？如果我已经完成 final int b = 2 ，一切正常。

Why am I getting this sort of error? If I would have done final int b = 2, everything works.

推荐答案

b 可能尚未初始化，并且可以为其分配多个值。在您的示例中，它显然已初始化，但可能编译器无法知道（并且它不能）。想象一下：

b may not have been initialized and it is possible to be assigned multiple values. In your example it is obviously initialized, but probably the compiler doesn't get to know that (and it can't). Imagine:

final int b;
if (something) {
   b = 1;
} else {
   b = 2;
}

编译器需要开关中的常量，但 b 的值取决于某些外部变量。

The compiler needs a constant in the switch, but the value of b depends on some external variable.

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