CSIT 115 Class 2 Exercise: Finding and Using an API   

                                                                         Name:__________________

// A robust two-digit number-guessing game with hinting. Page 354.

import java.util.*;

public class NumberGuess3 {

    public static void main(String[] args) {

        giveIntro();

        Scanner console = new Scanner(System.in);

        // pick a random number from 0 to 99 inclusive

        Random rand = new Random();

        int number = rand.nextInt(100);

        // get first guess

        int guess = getGuess(console);

        int numGuesses = 1;

        // give hints until correct guess is reached

        while (guess != number) {

            int numMatches = matches(number, guess);

            System.out.println("Incorrect (hint: " +

                               numMatches + " digits match)");

            guess = getGuess(console);

            numGuesses++;

        }   

        System.out.println("You got it right in " +

                           numGuesses + " tries.");

    }

    // Displays an introduction message to the user.

    public static void giveIntro() {

        System.out.println("Try to guess my two-digit");

        System.out.println("number, and I'll tell you how");

        System.out.println("many digits from your guess");

        System.out.println("appear in my number.");

        System.out.println();

    }

    // Returns # of matching digits between the two numbers.

    // pre: number and guess are unique two-digit numbers

    public static int matches(int number, int guess) {

        int numMatches = 0;

        if (guess / 10 == number / 10 ||

            guess / 10 == number % 10) {

            numMatches++;

        }      

        if (guess / 10 != guess % 10 &&

            (guess % 10 == number / 10 ||

             guess % 10 == number % 10)) {

            numMatches++;

        }   

        return numMatches;

    }

    // Re-prompts until a number in proper range is entered.

    // post: guess is between 0 and 99

    public static int getGuess(Scanner console) {

        int guess = getInt(console, "Your guess? ");

        while (guess < 0 || guess >= 100) {

            System.out.println("Out of range; try again.");

            guess = getInt(console, "Your guess? ");

        }

        return guess;

    }

    // Re-prompts until a number is entered.

    public static int getInt(Scanner console, String prompt) {

        System.out.print(prompt);

        while (!console.hasNextInt()) {

            console.next();

            System.out.println("Not an integer; try again.");

            System.out.print(prompt);

        }

        return console.nextInt();

    }

}

1. Write down the rest of the API in use by main to utilize the other methods in this program. An API is a set of method headers. Here’s one:

     // Displays an introduction message to the user.

public static void giveIntro()

2. Underline the calls to the API in main.

3. Show a call to matches that checks if a user guess of 43 matches a secret number of 63.  What is the return value?

4. Show a call to getGuess using a Scanner named myScanner.

5. Show what appears on the screen for the call in 3, assuming the user types 43 and then carriage return.