Concerning the first question..., what I asking is if there is sample code in the book for the exercise 5-4? Here is the exercise.
Creating an exception
In this exercise we attempt to create a custom exception. We won't put in any new
methods (it will have only those inherited from Exception), and because it extends
Exception, the compiler considers it a checked exception. The goal of the program
is to determine whether a command-line argument, representing a particular food
(as a string), is considered bad or OK.
* Let's first create our exception. We will call it BadFoodException. This excep-
tion will be thrown when a bad food is encountered.
* Create an enclosing class called MyException and a main() method,
which will remain empty for now.
* Create a method called checkFood(). It takes a String argument and throws
our exception if it doesn't like the food it was given. Otherwise, it tells us it likes
the food. You can add any foods you aren't particularly fond of to the list.
* Now in the main() method, you'll get the command-line argument out of the
String array, and then pass that String on to the checkFood() method.
Because it's a checked exception, the checkFood() method must declare it, and
the main() method must handle it (using a try/catch). Do not have main()
declare the exception, because if main() ducks the exception, who else is back
there to catch it?
* As nifty as exception handling is, it's still up to the developer to make proper
use of it. Exception handling makes organizing our code and signaling problems
easy, but the exception handlers still have to be written. You'll find that even
the most complex situations can be handled, and your code will be reusable,
readable, and maintainable.
I did a quick look through of my book (having the same one) and didn't see any example code of this. However, I don't think it is too complicated, and I think if you googled "java extend Exception" you should find some examples.
When I die, I want people to look at me and say "Yeah, he might have been crazy, but that was one zarkin frood that knew where his towel was."