Task: Bulls and cows_Player
C++: #include <iostream>
#include <sstream>
#include <iomanip>
#include <algorithm>
#include <vector>
#include <time.h>


using namespace std;


const unsigned int LEN = 4;


class CowsAndBulls_Player
{
public:
    CowsAndBulls_Player() { fillPool(); }
    void play() { secret = createSecret(); guess(); }

private:
    void guess()
    {
	pair<int, int> res; int cc = 1;
	cout << endl << " SECRET: " << secret << endl << "==============" << endl;
	cout << "+-----------+---------+--------+\n|   GUESS   |  BULLS  |  COWS  |\n+-----------+---------+--------+\n";
	while( true )
	{
	    string gs = gimmeANumber();
	    if( gs.empty() ) { cout << endl << "Something went wrong with the scoring..." << endl << "Cannot find an answer!" << endl; return; }
	    if( scoreIt( gs, res ) ) { cout << endl << "I found the secret number!" << endl << "It is: " << gs << endl; return; }
	    cout << "|    " << gs << "   |  " << setw( 3 ) << res.first << "    |  " << setw( 3 ) << res.second << "   |\n+-----------+---------+--------+\n";
	    clearPool( gs, res );
        }
    }

    void clearPool( string gs, pair<int, int>& r )
    {
	vector<string>::iterator pi = pool.begin();
	while( pi != pool.end() )
	{
	    if( removeIt( gs, ( *pi ), r ) ) pi = pool.erase( pi );
	    else  pi++;
	}
    }

    string gimmeANumber()
    {
	if( pool.empty() ) return "";
	return pool[rand() % pool.size()];
    }

    void fillPool()
    {
	for( int x = 1234; x < 9877; x++ )
	{
	    ostringstream oss; oss << x;
	    if( check( oss.str() ) ) pool.push_back( oss.str() );
	}
    }

    bool check( string s )
    {
	for( string::iterator si = s.begin(); si != s.end(); si++ )
	{
	    if( ( *si ) == '0' ) return false;
	    if( count( s.begin(), s.end(), ( *si ) ) > 1 ) return false;
	}
	return true;
    }

    bool removeIt( string gs, string ts, pair<int, int>& res )
    {
	pair<int, int> tp; getScore( gs, ts, tp );
	return tp != res;
    }

    bool scoreIt( string gs, pair<int, int>& res )
    {
	getScore( gs, secret, res );
	return res.first == LEN;
    }

    void getScore( string gs, string st, pair<int, int>& pr )
    {
	pr.first = pr.second = 0;
	for( unsigned int ui = 0; ui < LEN; ui++ )
	{
	    if( gs[ui] == st[ui] ) pr.first++;
	    else
	    {
		for( unsigned int vi = 0; vi < LEN; vi++ )
		    if( gs[ui] == st[vi] ) pr.second++;
	    }
	}
    }

    string createSecret()
    {
	string n = "123456789", rs = "";
	while( rs.length() < LEN )
	{
	    int r = rand() % n.length();
	    rs += n[r]; n.erase( r, 1 );
	}
	return rs;
    }

    string secret;
    vector<string> pool;
};

int main( int argc, char* argv[] )
{
    srand( static_cast<unsigned int>( time( NULL ) ) ); CowsAndBulls_Player cb;
    cb.play(); cout << endl << endl;
    return system( "pause" );
}


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();
    }
}