Exception Handling - Java - page 492

Self-Test Exercises (continued)
public DoubleException( double number)
{
super ("DoubleException thrown!");
doubleMessage = number;
}

public double getNumber()
{
return doubleMessage;
}
}

What output would be produced by the following code (which is just an exercise and
not likely to occur in a program)?

DoubleException e =
new DoubleException(41.9);

System.out.println(e.getNumber());
System.out.println(e.getMessage());

The class DoubleException is on the CD that comes with this text.
18. There is an exception class named IOException that is defined in the standard Java
libraries. Can you define an exception class as a derived class of the predefined class
IOException , or must a defined exception class be derived from the class Exception ?

extra code
on CD

Multiple catch Blocks
A try block can potentially throw any number of exception values, and they can be of
differing types. In any one execution of the try block, at most one exception will be
thrown (since a throw statement ends the execution of the try block), but different
types of exception values can be thrown on different occasions when the try block is
executed. Each catch block can only catch values of the exception class type given in
the catch block heading. However, you can catch exception values of differing types by
placing more than one catch block after a try block. For example, the program in Dis-
play 9.7 has two catch blocks after its try block. The class NegativeNumberException ,
which is used in that program, is given in Display 9.8.

Display 9.7 Catching Multiple Exceptions (part 1 of 3)

1 import java.util.Scanner;

2 public class MoreCatchBlocksDemo
3{
4 public static void main(String[] args)
5

{

6 Scanner keyboard = new Scanner(System.in);

7