CSIS 110 - Lecture 12
Lab Comments
Discuss isEmpty() method: most people had something like:
if ( notes.size() == 0 ) // or ( numberOfNotes() == 0 )
{
return true;
}
else
{
return false;
}
Discuss simplifying this.
ArrayList
Last time we looked at the ArrayList class, which is provided by the Java library. It is a
type of Collection, which means that it can be used to store objects of some other type.
What are some of the methods provided by the ArrayList?
add – store an object at the end of the list
size – return the number of objects in the list
get – get an object from the list (but don’t remove it)
Properties of ArrayLists:
Variable size – an ArrayList gets bigger if necessary as we add more items
It keeps track of the number of items it currently contains
It maintains the order of the items.
The ArrayList is an example of a generic or parameterized class. This means that when
we create an ArrayList object, we have to specify the type of objects that will be stored in
the ArrayList.
Let's look at some other declarations:
private ArrayList<String> notes;
private ArrayList<MailItem> inbox;
private ArrayList<Book> library;
What is the type of the variable? What is the type of the elements being stored in the
ArrayList?
