Trying to call a method from a subclass using the super class's object in a whole different class

This is my method. Type schedule is an array list using the Class Activity. However, the method getName and getSection are both in Activities subclass and a.getName(); and a.getSection() are both failing. Hopefully someone can help me!

public String[][] getScheduledActivities() {
    String [][] scheduledCourse;
    if (schedule.size() == 0) {
        scheduledCourse = new String[0][0];
    } else {
        scheduledCourse = new String[schedule.size()][3];
        for (int i = 0; i < schedule.size(); i++) {
            Activity a = schedule.get(i);
            scheduledCourse[i] = a.getShortDisplayArray();
            scheduledCourse[i][0] = a.getName();
            scheduledCourse[i][1] = a.getSection();
            scheduledCourse[i][2] = a.getTitle();                   
        }
    }
    return scheduledCourse;
}