Exception Handling - Absolute Java - page 541

of a String instance variable that can later be recovered with a call to getMessage .
The method getMessage is an ordinary accessor method of the class Exception . The
class DivisionByZeroException inherits this String instance variable as well as the
accessor method getMessage .
For example, in Display 9.5, we give a sample program that uses this exception class.
The exception is thrown using the no-argument constructor, as follows:

throw new DivisionByZeroException();

Display 9.4 A Programmer-Dei ned Exception Class

1 public class DivisionByZeroException extends Exception
2 {
3 public DivisionByZeroException()
4 {
5

You can do more in an exception
constructor, but this form is
common.

super ("Division by Zero!");

6 }

7 public DivisionByZeroException(String message)
8 {
9

super is an invocation of the constructor
for the base class Exception .

super (message);

10 }
11 }

Display 9.5 Using a Programmer-Dei ned Exception Class (part 1 of 3)

1 import java.util.Scanner;

We will present an improved version of this
program later in this chapter in Display 9.10.

2 public class DivisionDemoFirstVersion
3 {

4 public static void main(String[] args)
5 {
6 try
7 {
8 Scanner keyboard = new Scanner(System.in);

9 System.out.println("Enter numerator:");
10 int numerator = keyboard.nextInt();
11 System.out.println("Enter denominator:");
12 int denominator = keyboard.nextInt();

(continued)