Task: Bulls and cows_Player
Go: package main

import (
    "bufio"
    "fmt"
    "os"
    "strconv"
    "strings"
)

func main() {
    fmt.Println(`Cows and bulls/player
You think of four digit number of unique digits in the range 1 to 9.
I guess.  You score my guess:
    A correct digit but not in the correct place is a cow.
    A correct digit in the correct place is a bull.
You give my score as two numbers separated with a space.`)

    
    m := make(map[string]int)
    var g func([]byte, int)
    g = func(digits []byte, fixed int) {
        if fixed == 4 {
            m[string(digits[:4])] = 0
            return
        }
        for i := fixed; i < len(digits); i++ {
            digits[fixed], digits[i] = digits[i], digits[fixed]
            g(digits, fixed+1)
            digits[fixed], digits[i] = digits[i], digits[fixed]
        }
    }
    g([]byte("123456789"), 0)

    
    for in := bufio.NewReader(os.Stdin);; {
        
        var guess string
        for guess = range m {
            delete(m, guess)
            break
        }

        
        var c, b uint
        for ;; fmt.Println("Score guess as two numbers: cows bulls") {
            fmt.Printf("My guess: %s.  Score? (c b) ", guess)
            score, err := in.ReadString('\n')
            if err != nil {
                fmt.Println("\nSo, bye.")
                return
            }
            s2 := strings.Fields(score)
            if len(s2) == 2 {
                c2, err := strconv.ParseUint(s2[0], 10, 0)
                if err == nil && c2 <= 4 {
                    b2, err := strconv.ParseUint(s2[1], 10, 0)
                    if err == nil && c2+b2 <= 4 {
                        c = uint(c2)
                        b = uint(b2)
                        break
                    }
                }
            }
        }

        
        if b == 4 {
            fmt.Println("I did it. :)")
            return
        }

        
        for pat := range m {
            var cows, bulls uint
            for ig, cg := range guess {
                switch strings.IndexRune(pat, cg) {
                case -1:
                default: 
                    cows++
                case ig:
                    bulls++
                }
            }
            if cows != c || bulls != b {
                delete(m, pat)
            }
        }

        
        if len(m) == 0 {
            fmt.Println("Oops, check scoring.")
            return
        }
    }
}

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();
    }
}