public static void main(String[] args) {
volidyYanMa(printYanMa());
}
public static String printYanMa(){
Random r=new Random();
char[] result=new char[4];
for (int i = 0; i < result.length; i++) {
int n=r.nextInt(26)+65;
char c=(char)n;
result[i]=c;
}
return new String(result);
}