OJ Board

I think you're not giving importance to a little detail:
"4. and repeat these steps unless the new number has already appeared in the chain"

You gotta verify if the number has already appeared on the chain, so, you gotta have a register of each number and search the new number. That's all you need ...

I can't understand why I got a compile error, this is my code:

import java.io.IOException;
import java.util.StringTokenizer;

/**
* Solucion al problema 340 Master-Mind Hints.
* @author Gabriel Rivera Safadi
*/
class Main {

static String readLine() {
int car = -1;
String s = "";
try ...