“if”语句末尾的分号 [英] Semicolon at end of 'if' statement

问题描述

今天，经过半小时的搜索错误，我发现可以在if语句后面加一个分号而不是代码，如下所示：

  if（a == b）; 
 //做东西
  

这基本上意味着无论是等于b，这些东西都会完成或不，if语句没有任何意义。为什么Java没有给我一个错误？有什么情况可以使用吗？

解决方案

为什么会这样？

Checkstyle

Pmd

他们可以立即突出显示此问题。

我建议结合两种解决方案。

Today, after half an hour of searching for a bug, I discovered that it is possible to put a semicolon after an if statement instead of code, like this:

if(a == b);
// Do stuff

Which basically means that the stuff will be done whether a equals b or not, and the if statement has no point whatsoever. Why doesn't Java give me an error? Is there any situation in which this would be useful?

解决方案

Why does it happen?

Java Language Specification says that:

The Empty Statement

An empty statement does nothing.

EmptyStatement:
    ;

Execution of an empty statement always completes normally

It essentially means that you want to execute empty statement if a==b

if(a == b);

What should you do:

There are two main solutions to this problem:

1. You can avoid problems with empty statement by using code formatter and surrounding stuff inside if with { and }. By doing this Your empty statement will be much more readable.

   if(a == b){
     ;
   }
   

2. You can also check tools used for static code analysis such as:

   • Findbugs
   • Checkstyle
   • Pmd

   They can instantly highlight problems such as this one.

I would recommend to combine both solutions.

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