User u1 = null ;
long cursor = -1;
IDs ids;
System.out.println("Listing followers's ids.");
do {
ids = twitter.getFollowersIDs("username", cursor);
for (long id : ids.getIDs()) {
System.out.println(id);
User user = twitter.showUser(id);
System.out.println(user.getName());
}
} while ((cursor = ids.getNextCursor()) != 0);
Take a look: Friends list of a friend using Twitter4J