Java 开关:变量声明和作用域 [英] Java switch : variable declaration and scope

问题描述

Java 编译器如何处理以下开关块?'b' 变量的作用域是什么?

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.尝试在第二个分支中声明它也会导致重复局部变量"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:以上代码使用 java 1.6 编译器编译.

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

推荐答案

范围和往常一样，由 { 和 } 分隔.

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

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