Guesser.java

import java.io.Console;
import java.util.Scanner;

/**
 * Assignment 1 - Guessing Game
 * 
 * Here's the unfinished source code for the Guesser class. It is your task to
 * complete the missing parts.
 */
public class Guesser {
	private int low;
	private int high;

	/*
	 * Task 1. Write code here for a constructor which takes two int arguments and
	 * saves them in the instance variables low and high.
	 *
	 * If you don't remember the syntax for how to write constructors, revisit the
	 * chapter "Classes" and review the section about constructors.
	 *
	 */

	// Write the constructor below this line.
	public Guesser(int low, int high) {
     this.low = low;
     this.high = high;
    }

	/*
	 * Task 2. Complete the start() method, so that in the method body, you call
	 * first the rules() method, next the doGuesses() method.
	 */
	public void start() {
		rules();
		doGuesses();
		// call the rules method here
		// call the doGuesses() method here
	}

	private void rules() {
		System.out.println("Think of a number between " + low + " and " + high);
		System.out.println("I'm going to ask a few questions in order " + "to guess the number.");
		System.out.println("Please answer T for true, and F for false.\n");
	}

	/*
	 * Task 3. Complete the code for the getReply() method. In the current version
	 * below, it returns null each call, which is not what this method is supposed
	 * to do.
	 * 
	 * Instead, change the method so that it reads a reply from the player, and if
	 * it is "T" or "F", we have a valid reply. Return the String that you read from
	 * the player.
	 */
	private String getReply() {
		Scanner scan = new Scanner (System.in);
		String reply = scan.nextLine();

		// Write code here which reads a String from the console.
		// As long as it is not a valid reply (one of "T" and "F")
		// write an error message, and read a new reply.
		// When you have gotten a valid reply, return it.
		while (!reply.equals("T") && !reply.equals("F")) {
			System.out.println("Error!");
			System.out.println("Please Answer T or F");
			reply = scan.nextLine();
		}
		return reply;
	}

	private void doGuesses() {
		int i = 0; // number of guesses
		int middle = 0;
		while (low < high) {
			// Set next guess to the middle between
			// current low and current high
			middle = low + (high - low) / 2;

			System.out.println("Is the number less than or equal to " + middle + "?");
			String reply = getReply();
			if ("T".equals(reply)) {
				// The number is less than or equal to middle
				// so we move down high to middle
				high = middle;
			} else {
				// The number is greater than middle,
				// so we move up low to middle + 1
				low = middle + 1;
			}
			i++; // One more guess!
		}
		// When low has met high, we don't enter the loop
		// and we have found the number
		answer(low, i);
	}

	private void answer(int guess, int numberOfGuesses) {
		System.out.println("You were thinking about " + guess + " (took me " + numberOfGuesses + " guesses)");
	}

}