java - Semicolon at end of 'if' statement

Question

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?

Answer 1

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.