Java开关：变量声明和范围 [英] Java switch : variable declaration and scope

问题描述

Java编译器如何处理以下交换机块？
'b'变量的范围是什么？

How does the Java compiler handle the following switch block ? What is the scope of the 'b' variable ?

请注意，'b'变量仅在switch语句的第一个分支中声明。试图在第二个分支中声明它也会导致重复的局部变量编译错误。

Note that the 'b' variable is declared only in the first branch of the switch statement. Attempting to declare it in the second branch as well results in a "duplicate local variable" compilation error.

    int a = 3;
    switch( a ) {
    case 0:
        int b = 1;
        System.out.println("case 0: b = " + b);
        break;
    case 1:
        // the following line does not compile: b may not have been initialized
        // System.out.println("case 1 before: b = " + b);
        b = 2;
        System.out.println("case 1 after: b = " + b);
        break;
    default:
        b = 7;
        System.out.println("default: b = " + b);
    }

注意：上面的代码用java 1.6编译器编译。

Note: the above code compiles with a java 1.6 compiler.

推荐答案

范围与正常情况一样，由 {和<$ c $分隔c>} 。

The scope is, just as usual, delimited by { and }.

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