Introduction to Parameters and Objects - Building Java Programs: A Back to Basics Approach - page 165

If a user types something that isn't an integer when you call nextInt , such as
XYZZY , the Scanner object generates an exception. Recall from the section on
String objects that exceptions are runtime errors that halt program execution. In this
case, you'll see runtime error output such as the following:
Exception in thread "main" java.util.InputMismatchException
at java.util.Scanner.throwFor(Unknown Source)
at java.util.Scanner.next(Unknown Source)
at java.util.Scanner.nextInt(Unknown Source)
at Example.main(Example.java:13)
You will see in a later chapter how to test for user errors. In the meantime, we will
assume that the user provides appropriate input.
Sample Interactive Program
Using the Scanner class, we can write a complete interactive program that performs a
useful computation for the user. If you ever find yourself buying a house, you'll want
to know what your monthly mortgage payment is going to be. The following is a com-
plete program that asks for information about a loan and prints the monthly payment:
1 // This program prompts for information about a loan and
2 // computes the monthly mortgage payment.
3
4 import java.util.*; // for Scanner
5
6 public class Mortgage {
7 public static void main(String[] args) {
8 Scanner console = new Scanner(System.in);
9
10 // obtain values
11 System.out.println("This program computes monthly " +
12 "mortgage payments.");
13 System.out.print("loan amount : ");
14 double loan = console.nextDouble();
15 System.out.print("number of years : ");
16 int years = console.nextInt();
17 System.out.print("interest rate : ");
18 double rate = console.nextDouble();
19 System.out.println();
20
21 // compute result and report
22 int n = 12 * years;
23 double c = rate / 12.0 / 100.0;