Java can be fun!

SchoolClass.java

List<Student> studentsWhoHaveNotTakenAtLeastOneTest() {
  List<Student> allStudents = this.getStudents().clone(); /* shallow copy to avoid mutation */
  Iterator<Student> studentIt = allStudents.iterator();

  /* select down to students missing at least one test */
  List<Student> studentsMissingAtLeastOneTest = new ArrayList<Student>();


  for(Student student : studentIt) {
    List<Test> tests = student.getTests(); /* no shallow copy this time */
    if (tests.equals(null) || (tests.size == 0)) {
      continue;
    } else {
      boolean shouldSelectThisStudent = false;
      Iterator<Tests> testIt = tests.iterator();
      for(Test test : testIt) {
        /* many Java programmers would short circuit this -- I don't usually do that.*/
        shouldSelectThisStudent = shouldSelectThisStudent || (!test.isTaken());
      }

      if (shouldSelectThisStudent) {
        studentsMissingAtLeastOneTest.addLast(student);
      }
    }     
  }

  /* now sort by last name */
  Comparator<Student> lastNameSorter = new Comparator<Student,Student> {
    public int compare(Student student1, Student student2) {
      return student1.getLastName().compare(student2.getLastName()); /* dangerous code, please don't template off this, but it's legion in the field */
    }
  }

  return studentsMissingAtLeastOneTest.sort(lastNameSorter);

}