iCal4j neznám, ale chápu-li správně o co se tady snažíš, tak bych to udělal následovně:

public class MyEvent implements Comparable<MyEvent> {

    private VEvent event;

    public MyEvent (VEvent event) {
         this.event = event;
    }
   
    // muzes si i v pripade nutnost "zviditelnit" i ostani metody VEventu v MyEventu prostym delegovanim volani
 
    public VEvent getVEvent() { return this.event; }

    public int compareTo( MyEvent myEvent ) {
        // implementace porovnavaci metody 
        // k 1. VEeventu se dostanes pres field event k 2. pres myEvent.getVEvent()
    }
}

public static TreeSet<MyEvent> loadEvents(InputStreamReader input) throws IOException, ParserException{
		TreeSet<MyEvent> events = new TreeSet<MyEvent>();
		CalendarBuilder builder = new CalendarBuilder();
		Calendar calendar = builder.build(input);
		ComponentList cl = calendar.getComponents(Component.VEVENT);
	        VEvent event;
		//String summary;
		//Property property;
		for(int i = 0 ; i < cl.size() ; i++){
			event = (VEvent) cl.get(i);
			//summary = event.getProperty(Property.SUMMARY).getValue();
			//System.out.print(summary);
			//property = event.getProperty(Property.RRULE);
			//if(property != null){

			//}
			//System.out.println(event.toString());
			events.add(new MyEvent(event));
		}