recursive
import java.util.HashMap;
class S{
public static HashMap<Integer, String> map = new HashMap<>();
public String convertTo16(int num) {
if (num < 16){
return map.get(num) + "";
}
return convertTo16(num / 16) + map.get(num % 16);
}
public static void main(String[] args) {
S s = new S();
for(int i =0; i<10;i++){
map.put(i, Integer.toString(i));
}
map.put(10,"A");
map.put(11,"B");
map.put(12,"C");
map.put(13, "D");
map.put(14,"E");
map.put(15,"F");
String ans = s.convertTo16(110);
System.out.println(ans);
}
}