```
public String getHint(String secret, String guess) {
if(secret== null || guess == null || secret.length() != guess.length()){
return "wrong input";
}
int[] number_secret = new int[10];
int[] number_guess = new int[10];
int A = 0;
int B = 0;
for(int i = 0; i < secret.length(); i++){
if(secret.charAt(i) == guess.charAt(i)){
A++;
}else{
number_secret[secret.charAt(i) -'0']++;
number_guess[guess.charAt(i) -'0']++;
}
}
for(int i = 0; i < number_secret.length; i++){
B += Math.min(number_secret[i], number_guess[i]);
}
return A+"A"+B+"B";
}
```
```