What is throwable

[Sean Kelly]

Steve Teale wrote:
> 
> What is the point of class Throwable if you can throw any old class object?

I think a case could be made for allowing only children of Throwable to 
be thrown.  It's possible to throw integers and strings in C++, for 
example, which is totally ridiculous.  However, at the moment Throwable 
simply serves as the common base class for Exception and Error, and 
holds file and line info as well as the stack trace hooks.