NPE

Type safety without null safety is like a biohazard suit with an open face.

This is very typical Java code. It exhibits obnoxiously verbose typing, and yet can crash your application with NullPointerExceptions at runtime.

SuperDatabaseConnector superDatabaseConnector = SuperDatabaseConnector.getInstance();

getResultsFrom(superDatabaseConnector);

public static SomethingElseButMaybeNull getResultsFrom(SuperDatabaseConnector superDatabaseConnector) {
  return superDatabaseConnector.getResults();
}

Java is a bad language and you shouldn't use it.