为什么Java仅在while循环的情况下识别无法访问的代码？ [英] Why Java identifies unreachable code only in case of while loop?

问题描述

如果我有像

public static void main(String args[]){
    int x = 0;
    while (false) { x=3; }  //will not compile  
}

编译器会投诉 x = 3 是无法访问的代码，但如果我有代码

compiler will complaint that x=3 is unreachable code but if I have code like

public static void main(String args[]){
    int x = 0;
    if (false) { x=3; }
    for( int i = 0; i< 0; i++) x = 3;   
}

然后通过 if语句中的代码正确编译和 for loop 无法访问。为什么java工作流逻辑没有检测到这种冗余？任何用例？

then it compiles correctly though the code inside if statement and for loop is unreachable. Why is this redundancy not detected by java workflow logic ? Any usecase?

推荐答案

如 Java语言规范，此功能保留用于条件编译。

As described in Java Language Specification, this feature is reserved for "conditional compilation".

JLS中描述的一个例子是你可能有一个常量

An example, described in the JLS, is that you may have a constant

static final boolean DEBUG = false;

以及使用此常量的代码

if (DEBUG) { x=3; }

想法是提供更改 DEBUG 从 true 到 false 轻松不对代码进行任何其他更改，如果上面的代码给出了编译错误。

The idea is to provide a possibility to change DEBUG from true to false easily without making any other changes to the code, which would not be possible if the above code gave a compilation error.

这篇关于为什么Java仅在while循环的情况下识别无法访问的代码？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！