Indonesia consists of hundreds of distinct native ethnic and linguistic groups. However, the largest − and politically dominant − ethnic group are the Javanese. A shared identity has developed, defined by a national language, ethnic diversity, religious pluralism within a majority Muslim population, and a history of colonialism and rebellion against it.
It is also need to consider not to visit Indonesia during the holiday festive, specially a Muslim holiday Eid (both Eid Fitr or Eid Adh) since the transportation will be so full and the traffic tends to be heavy especially in Java island. Unless you are interested in seeing the festivals up close and experiencing them, of course then it worth to see the warmest feeling full in the air and in the heart of Indonesian people.