1)One way of implementing a calendar is as a map from date objects to event objects. However, that only works if there is a single event for a given date. How can you use another collection type to allow for multiple events on a given date?

2)Look up the descriptions of the methods addAll, removeAll, retainAll, and containsAll in the Collection interface. Describe how these methods can be used to implement common operations on sets (union, intersection, difference, subset).

3)Explain what the following code prints. Draw a picture of the linked list after each step.

LinkedList staff = new LinkedList<>(); staff.addFirst("Harry"); staff.addFirst("Diana"); staff.addFirst("Tom"); System.out.println(staff.removeFirst()); System.out.println(staff.removeFirst()); System.out.println(staff.removeFirst());