[Java] Using a nested for loop or nested while loop fails to iterate through all elements REFACTOR

CourseUtils.java

public boolean detectConflict(Course aCourse) { //FIXME
  boolean foundConflict = false;
    for (Course existingCourse : schedule) {
      for (Integer timeofNewCourse : aCourse.getSchedule()) {
        for (Integer timeofExistingCourse : existingCourse.getSchedule()) {
            if (timeofExistingCourse.equals(timeofNewCourse)) {
              System.out.print(String.format("%s%d course cannot be added to %s's schedule. ",
                                             aCourse.getDepartment().getDepartmentName(),
                                             aCourse.getCourseNumber(),
                                             this.getName()));

              System.out.println(String.format("%s%d conflicts with %s%d. Conflicting time slot is : %s %s",
                                               aCourse.getDepartment().getDepartmentName(),
                                               aCourse.getCourseNumber(),
                                               existingCourse.getDepartment().getDepartmentName(),
                                               existingCourse.getCourseNumber(),
                                               convertCourseNumToDayofWeek(aCourse.getCourseNumber()),
                                               convertCourseNumToTime(aCourse.getCourseNumber())));

           foundConflict = true;
        }
      }
    }
  }
 return foundConflict;
}

private String convertCourseNumToTime(int courseNum) {
  switch (courseNum % 100) {
    case 1:
      return "8:00am to 9:15am.";
    case 2:
      return "9:30am to 10:45am.";
    case 3:
      return "11:00am to 12:15pm.";
    case 4:
      return "12:30pm to 1:45pm.";
    case 5:
      return "2:00pm to 3:15pm.";
    case 6:
      return "3:30pm to 4:45pm.";
  }
  return "";
}

private String convertCourseNumToDayofWeek(int courseNum) {
  switch (courseNum / 100) {
    case 1:
      return "Mon";
    case 2:
      return "Tue";
    case 3:
      return "Wed";
    case 4:
      return "Thu";
    case 5:
      return "Fri";
   }
   return "";
}

public void printSchedule() {
  for (Course course : schedule) {
    for (Integer courseNumber : course.getSchedule()) {
      System.out.println(String.format("%s %s %s%d %s",
                                       convertCourseNumToDayofWeek(courseNumber),
                                       convertCourseNumToTime(courseNumber),
                                       course.getDepartment().getDepartmentName(),
                                       course.getCourseNumber(),
                                       course.getName()));
    }
  }
}