Java ArrayLists

1
Java ArrayLists

• Gary Greer

2
What Are ArrayLists?

• ArrayLists are data storage objects that
• are unlimited in size
• perform much of the programming for you
• also allow you to sort data
• based on the idea of a list of elements
• basically you just add, remove, retrieve elements
  from the list without worrying about the size
  (arrays need to be a defined size)

3
Defining and Creating

• requires import java.util.
• defining
• ArrayList myList
• creating
• myList new ArrayList
• simple as that

4
ArrayLists Contain Objects

• can only use objects, so define one
• class cat ()
• String name
• public cat (String n)
• name n
• public String getName ()
• return name
• public void setName (String n)
• name n

5
Adding Data

• pretty simple
• create a new object, and then add it to the end
  of the list
• myCat new Cat ("Stuffy")
• myList.add(myCat)
• you can also add to a particular place in the
  list
• myCat new Cat ("Stuffy")
• myList.add(3, myCat)

6
Removing Data

• pretty simple again
• remove the first element
• myList.remove(0)
• remove the last element
• myList.remove(myList.size() - 1)

7
Retrieving Data

• simple again
• get the first element
• myList.get(0)
• get the last element
• myList.get(myList.size() - 1)

8
Working With The Entire List

• often we need to work with the entire list
• for example we might want to print it
• we use for statements to do this
• for (int index 0 index lt myList.size()
  index)
• myCat (Cat) myList.get(index)
• System.out.print(myCat.getName() "
  ")

9
Notes

• there are much more sophisticated and powerful
  ways to work with ArrayLists
• iterators are often used to step through the data
• sorting is possible
• different types of objects may be stored in the
  same list

10
References

• Eckel, B. (2003). Thinking in Java. Retrieved
  from www.BruceEckel.com
• Sun MicroSystems (2005). Java APIs. Retrieved
  from http//java.sun.com/j2se/1.5.0/docs/api/index
  .html