MATHEMATICAL FUNCTIONS, CHARACTERS, AND STRINGS - Introduction to Java Programming: Comprehensive Version - page 144

if ch is 'B' , and so on. When two characters perform a numerical operation, the characters'
Unicodes are used in the computation.
The program invokes the Character.isDigit(ch) method to check if ch is between
'0' and '9' (line 22). If so, the corresponding decimal digit is the same as ch (lines 23-24).
If ch is not between 'A' and 'F' nor a digit character, the program displays an error message
(line 27).

4.5.3 Case Study: Revising the Lottery Program Using Strings
The lottery program in Listing 3.8, Lottery.java, generates a random two-digit number, prompts
the user to enter a two-digit number, and determines whether the user wins according to the
following rule:

1. If the user input matches the lottery number in the exact order, the award is $10,000.

2. If all the digits in the user input match all the digits in the lottery number, the award is
$3,000.

3. If one digit in the user input matches a digit in the lottery number, the award is $1,000.

The program in Listing 3.8 uses an integer to store the number. Listing 4.5 gives a new
program that generates a random two-digit string instead of a number and receives the user
input as a string instead of a number.

L ISTING 4.5

LotteryUsingStrings.java
1 import java.util.Scanner;
2
3 public class LotteryUsingStrings {
4 public static void main(String[] args) {
5 // Generate a lottery as a two-digit string
6 String lottery = "" + ( int )(Math.random() * 10 )
7 + ( int )(Math.random() * 10 );
8
9 // Prompt the user to enter a guess
10 Scanner input = new Scanner(System.in);
11 System.out.print( "Enter your lottery pick (two digits): " );
12 String guess = input.nextLine();
13
14

generate a lottery

enter a guess

// Get digits from lottery

15 char lotteryDigit1 = lottery.charAt( 0 );

16 char lotteryDigit2 = lottery.charAt( 1 );

17
18

// Get digits from guess

19 char guessDigit1 = guess.charAt( 0 );

20 char guessDigit2 = guess.charAt( 1 );

21
22 System.out.println( "The lottery number is " + lottery);
23
24 // Check the guess
25 if (guess.equals(lottery))
26 System.out.println( "Exact match: you win $10,000" );
27 else if (guessDigit2 == lotteryDigit1
28 && guessDigit1 == lotteryDigit2)
29 System.out.println( "Match all digits: you win $3,000" );
30 else if (guessDigit1 == lotteryDigit1
31 || guessDigit1 == lotteryDigit2
32 || guessDigit2 == lotteryDigit1
33 || guessDigit2 == lotteryDigit2)
34 System.out.println( "Match one digit: you win $1,000" );

exact match?

match all digits?

match one digit?