Challenge115 Easy http://www.reddit.com/r/dailyprogrammer/comments/15ul7q/122013_challenge_115_easy_guessthatnumber_game/

Challenge115.java

import java.util.InputMismatchException;
import java.util.Random;
import java.util.Scanner;

public abstract class Challenge115 {
  /**
	 * Binary Search Robot
	 * 
	 * @author SplashAttacks
	 */
	private static class RobotInputChallenge115 extends Challenge115 {
		private Integer lastGuess = null;
		private int max;
		private int min = 1;

		public RobotInputChallenge115(int range) {
			super(range);
			max = range;
		}

		@Override
		protected int getGuess() {
			if (hasGuessed()) {
				if (lastGuess < getNumber()) {
					min = lastGuess;
				} else if (lastGuess > getNumber()) {
					max = lastGuess;
				} else {
					min = lastGuess;
					max = lastGuess;
				}
			}
			int guess = ((max - min) / 2) + min;
			// Fix for edge case, we should never guess the same number twice
			// Happens because we are flooring fractional numbers.
			if (hasGuessed() && guess == this.lastGuess) {
				guess++;
			}

			lastGuess = guess;

			return guess;
		}

		private boolean hasGuessed() {
			return lastGuess != null;
		}

		@Override
		protected boolean playAgain() {
			return false;
		}

	}

	private static class UserInputChallenge115 extends Challenge115 {
		private final Scanner scanner = new Scanner(System.in);

		public UserInputChallenge115(int range) {
			super(range);
		}

		@Override
		protected int getGuess() {
			Integer guess = null;
			do {
				try {
					guess = scanner.nextInt();
					if (guess < 1 || guess > getRange()) {
						System.out
								.println("Please entery an integer between 1 and "
										+ getRange() + ".");
					}
				} catch (InputMismatchException ime) {
					System.out
							.println("Please entery an integer between 1 and "
									+ getRange() + ".");
					// Throw away the non integer from the scanner.
					scanner.next();
				}
			} while (guess == null || guess < 1 || guess > getRange());
			return guess;
		}

		@Override
		protected boolean playAgain() {
			System.out.println("Play Again (y/n)? ");
			Boolean result = null;
			do {
				String selection = scanner.next().toLowerCase();
				if (selection.equals("y") || selection.equals("yes")) {
					result = true;
				} else if (selection.equals("n") || selection.equals("no")) {
					result = false;
				} else {
					System.out.println("Play Again (y/n)? ");
				}
			} while (result == null);

			if (!result) {
				scanner.close();
			}

			return result;
		}
	}

	public static void main(String[] args) {
		// Challenge115 challenge = new RobotInputChallenge115(100);
		Challenge115 challenge = new UserInputChallenge115(100);
		challenge.play();
	}

	private int number;
	private final Random random;
	private int range;

	public Challenge115(int range) {
		this.random = new Random();
		this.range = range;
	}

	public int getNumber() {
		return number;
	}

	public int getRange() {
		return range;
	}

	protected abstract int getGuess();

	private void play() {
		boolean playAgain = true;
		while (playAgain) {
			number = thinkOfANumber();
			System.out
					.println("Welcome to guess-that-numbers game! I have already picked a number in [1, "
							+ range + "]. Please make a guess.");
			int tries = 0;
			int guess;
			do {
				guess = getGuess();
				tries++;
				if (guess < number) {
					System.out.println(guess
							+ " is wrong. That number is below my number.");
				} else if (guess > number) {
					System.out.println(guess
							+ " is wrong. That number is above my number.");
				}
			} while (guess != number);
			System.out.println(guess
					+ " is correct! That is my number, you win! It took you "
					+ tries + " tries.");
			playAgain = playAgain();
		}
		System.out.println("Thanks for playing!");
	}

	protected abstract boolean playAgain();

	private int thinkOfANumber() {
		return random.nextInt(range) + 1;
	}
}