What effect(s) did the closed-country policy have on japan?

In Japan the policy of closed country still has some effects. There is a sort of rule that makes people from abroad have six months to take Japanese classes, time to study and to get use to daily life in the country. However, some refugees that are affected by the rule have said that 6 months is a very short time to learn a language. Likewise, refugees must present an exam about their career, this exam will determined  if they can stay or they must return home.