Compiler doesn't complain when I ended a line with two semicolons. Why?

Question

I thought bad thing would happen when I ended a line like this. But compiler didn\'t even complain. Does anybody have an idea, why this is legal in java.

displ

Answer 1

Here's a practical example in C:

#ifndef NDEBUG
#define Dprintf printf
#else
#define Dprintf(X)
#endif

if(some_test)
   Dprintf("It's true!");
else
   Dprintf("It's false.");

If NDEBUG is defined, the compiler will see:

if(some_test)
   ;
else
   ;

This can be useful in some cases.

Since Java is heavily inspired by C/C++, it's something they kept, even though it is not useful and there is no preprocessor.

You can, if you want, run the C preprocessor cpp on your code to do this kind of behaviour.

Some languages may say it's an error instead, it's up to them to choose.