Можете да го направите по следния начин:
List<Student> students = new ArrayList<Student>();
BasicDBObject query = new BasicDBObject();
query.put("user", username);
DBCursor cursor = theCollection.find(query);
while (cursor.hasNext()) {
DBObject theObj = cursor.next();
//How to get the DBObject value to ArrayList of Java Object?
BasicDBList studentsList = (BasicDBList) theObj.get("students");
for (int i = 0; i < studentsList.size(); i++) {
BasicDBObject studentObj = (BasicDBObject) studentsList.get(i);
String firstName = studentObj.getString("firstName");
String lastName = studentObj.getString("lastName");
String age = studentObj.getString("age");
String gender = studentObj.getString("gender");
Student student = new Student();
student.setFirstName(firstName);
student.setLastName(lastName);
student.setAge(age);
student.setGender(gender);
students.add(student);
}
}