Japan was closed for over 200 years during the "Sakoku" period of Japanese history. During this time, it was illegal for any Japanese to leave the islands or for any foreigner to enter. The major benefit of this policy was increased stability. The policy prevented Christian missionaries from making converts and thus dividing Japan. It also denied some daimyo the ability to trade and thus become rich and strong enough to challenge the shogunate.
The main negative about this time was that it made Japan become somewhat backwards. By the time that Perry "opened" Japan at the end of this era, Japan lacked the technology and the general military and political systems needed to defend itself against the West. By isolating itself, Japan got stability, but paid for that stability by failing to modernize militarily, politically, and economically.