BulkExport.java

// Start listing users from the beginning, 1000 at a time.
ListUsersPage page = FirebaseAuth.getInstance().listUsersAsync(null).get();
while (page != null) {
  for (ExportedUserRecord user : page.getValues()) {
    System.out.println("User: " + user.getUid());
  }
  page = page.getNextPage();
}

// Iterate through all users. This will still retrieve users in batches,
// buffering no more than 1000 users in memory at a time.
page = FirebaseAuth.getInstance().listUsersAsync(null).get();
for (ExportedUserRecord user : page.iterateAll()) {
  System.out.println("User: " + user.getUid());
}