Task: Bulls and cows_Player
C#: using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace BullsAndCows
{
    class Program
    {
        const int ANSWER_SIZE = 4;

        static IEnumerable<string> Permutations(int size)
        {
            if (size > 0)
            {
                foreach (string s in Permutations(size - 1))
                    foreach (char n in "123456789")
                        if (!s.Contains(n))
                            yield return s + n;
            }
            else
                yield return "";
        }

        static IEnumerable<T> Shuffle<T>(IEnumerable<T> source)
        {
            Random random = new Random();
            List<T> list = source.ToList();
            while (list.Count > 0)
            {
                int ix = random.Next(list.Count);
                yield return list[ix];
                list.RemoveAt(ix);
            }
        }

        static bool ReadBullsCows(out int bulls, out int cows)
        {
            string[] input = Console.ReadLine().Split(',').ToArray();
            bulls = cows = 0;
            if (input.Length < 2)
                return false;
            else
                return int.TryParse(input[0], out bulls)
                    && int.TryParse(input[1], out cows);
        }

        static void Main(string[] args)
        {
            Console.WriteLine("Bulls and Cows");
            Console.WriteLine("==============");
            Console.WriteLine();
            List<string> answers = Shuffle(Permutations(ANSWER_SIZE)).ToList();
            while (answers.Count > 1)
            {
                string guess = answers[0];
                Console.Write("My guess is {0}. How many bulls, cows? ", guess);
                int bulls, cows;
                if (!ReadBullsCows(out bulls, out cows))
                    Console.WriteLine("Sorry, I didn't understand that. Please try again.");
                else
                    for (int ans = answers.Count - 1; ans >= 0; ans--)
                    {
                        int tb = 0, tc = 0;
                        for (int ix = 0; ix < ANSWER_SIZE; ix++)
                            if (answers[ans][ix] == guess[ix])
                                tb++;
                            else if (answers[ans].Contains(guess[ix]))
                                tc++;
                        if ((tb != bulls) || (tc != cows))
                            answers.RemoveAt(ans);
                    }
            }
            if (answers.Count == 1)
                Console.WriteLine("Hooray! The answer is {0}!", answers[0]);
            else
                Console.WriteLine("No possible answer fits the scores you gave.");
        }
    }
}

Java: public class BullsAndCowsPlayerGame {

    private static int count;
    private static Console io = System.console();

    private final GameNumber secret;
    private List<AutoGuessNumber> pool = new ArrayList<>();

    public BullsAndCowsPlayerGame(GameNumber secret) {
        this.secret = secret;
        fillPool();
    }

    private void fillPool() {
        for (int i = 123; i < 9877; i++) {
            int[] arr = AutoGuessNumber.parseDigits(i, 4);

            if (GameNumber.isGuess(arr)) {
                pool.add(new AutoGuessNumber(i, 4));
            }
        }
    }

    public void play() {
        io.printf("Bulls and Cows%n");
        io.printf("==============%n");
        io.printf("Secret number is %s%n", secret);

        do {
            AutoGuessNumber guess = guessNumber();
            io.printf("Guess #%d is %s from %d%n", count, guess, pool.size());

            GuessResult result = secret.match(guess);
            if (result != null) {
                printScore(io, result);

                if (result.isWin()) {
                    io.printf("The answer is %s%n", guess);
                    break;
                }

                clearPool(guess, result);
            } else {
                io.printf("No more variants%n");
                System.exit(0);
            }
        } while (true);
    }

    private AutoGuessNumber guessNumber() {
        Random random = new Random();
        if (pool.size() > 0) {
            int number = random.nextInt(pool.size());
            count++;
            return pool.get(number);
        }
        return null;
    }

    private static void printScore(Console io, GuessResult result) {
        io.printf("%1$d  %2$d%n", result.getBulls(), result.getCows());
    }

    private void clearPool(AutoGuessNumber guess, GuessResult guessResult) {
        pool.remove(guess);

        for (int i = 0; i < pool.size(); i++) {
            AutoGuessNumber g = pool.get(i);
            GuessResult gr = guess.match(g);

            if (!guessResult.equals(gr)) {
                pool.remove(g);
            }
        }
    }

    public static void main(String[] args) {
        new BullsAndCowsPlayerGame(new GameNumber()).play();
    }
}