Question: Sometimes when you are debugging, you have unreachable code fragment. Is there anyway to suppress the warning?

Answer: 
The only way to do this on any compiler is `@SuppressWarnings("all")`.

If you're using Eclipse, try `@SuppressWarnings("unused")`.
According to the [Java Language Specification](http://docs.oracle.com/javase/specs/jls/se7/html/jls-14.html#jls-14.21):

> 
> It is a compile-time error if a statement cannot be executed because it is unreachable.
> 
> 
> 

You can sometimes turn unreachable code into dead code (e.g., the body of `if (false) {...}`). But it being an error is part of the language definition.