EXCEPTION HANDLING AND TEXT I/O - Introduction to Java Programming: Comprehensive Version - page 454

done when an error occurs. The key benefit of exception handling is separating the detection
of an error (done in a called method) from the handling of an error (done in the calling
method).
Many library methods throw exceptions. Listing 12.5 gives an example that handles an
InputMismatchException when reading an input.

L ISTING 12.5

InputMismatchExceptionDemo.java
1 import java.util.*;
2
3 public class InputMismatchExceptionDemo {
4 public static void main(String[] args) {
5 Scanner input = new Scanner(System.in);
6

create a Scanner

boolean continueInput = true ;

7
8 do {
9 try {
10 System.out.print( "Enter an integer: " );
11

try block

int number = input.nextInt();

If an
InputMismatch
Exception
occurs

12
13 // Display the result
14 System.out.println(
15

"The number entered is " + number);

16
17 continueInput = false ;
18 }
19 catch (InputMismatchException ex) {
20 System.out.println( "Try again. (" +
21 "Incorrect input: an integer is required)" );
22 input.nextLine(); // Discard input
23 }
24 } while (continueInput);
25 }
26 }

catch block

Enter an integer: 3.5
Try again. (Incorrect input: an integer is required)
Enter an integer: 4
The number entered is 4

When executing input.nextInt() (line 11), an InputMismatchException occurs if
the input entered is not an integer. Suppose 3.5 is entered. An InputMismatchException
occurs and the control is transferred to the catch block. The statements in the catch block
are now executed. The statement input.nextLine() in line 22 discards the current input
line so that the user can enter a new line of input. The variable continueInput controls the
loop. Its initial value is true (line 6), and it is changed to false (line 17) when a valid input
is received. Once a valid input is received, there is no need to continue the input.

12.1

✓ ✓

What is the advantage of using exception handling?

Check

12.2

Point

Which of the following statements will throw an exception?

System.out.println( 1 / 0 );
System.out.println( 1.0 / 0 );