public void fillActivitiesTable() {
		activityService = ActivityService.getInstance();
		List<Activity> activities = activityService.getActivities();

		DefaultTableModel dtm = (DefaultTableModel) activitiesTable.getModel();
		for (int i = 0; i < dtm.getRowCount(); i++) {
			dtm.removeRow(i);
		}

		for (Activity activity : activities) {
			Object[] data = { activity.getName(), activity.getPlaces(),
					activity.getStudents().size(), activity.getPrize(),
					activity.getLicense() };
			dtm.addRow(data);
		}
		activitiesTable.updateUI();
	}