JAVA作業 猜數字的遊戲

import javax.swing.JOptionPane;


public class game {
public static void main(String[] args) {
String s=JOptionPane.showInputDialog("請輸入題目");
String d=JOptionPane.showInputDialog("請輸入答案");
int a=0;
int b=0;
for(int j=0;j<4;j++){
char c1 =d.charAt(j);
char c3 =s.charAt(j);
if(c1==c3){
a=a+1;
}else
for(int i=0;i<4;i++){
char c2=s.charAt(i);
if (c1==c2){
b=b+1;
}
}
}

System.out.println(a+"A");
System.out.println(b+"B");
}
}