Of course you probably know that for Muslims it is a must. In terms of tradition, for most Javanese boys, 11-12 years old is the time for the circumcision . I do not know much about other ethnic groups traditions for the time the boy to be circumcised. The Sundanese boys are circumcised younger than the Javanese boys, at about 5-6 years old.
Parents give their newly-circumcised sons a party on the day the boys are circumcised.
Their relatives, friends and, neighbors come to the party with presents or gifts for the boy. For the poorer families or the orphan boys, there's a collective circumcision ceremony and of course a collective but modest party that follows. Young boys regularly ask their parents repeatedly about the day they will be circumcised. They hope it will soon come so they can be big boys and get many presents. Because of this tradition, boys in Indonesia are used to seeing a circumcised penis.