ArrayLists and Iterators

1. ArrayLists and Iterators

Programs frequently keep data in lists. Often, arrays are used for this. Arrays are a fundamental feature of most programming languages. But because lists are so useful, Java includes the ArrayList class, which works much like an array with extra methods and features.

Like an array, an ArrayList contains elements that are accessed using an integer index. However, unlike an array, the size of an ArrayList is not fixed. An ArrayList expands as needed as items are added to it.

The class ArrayList is one of the standard classes that students are expected to know for the Advanced Placement test given in the United States. Every AP test for the past several years has included a programming problem involving this class.

Several of the features described in this chapter are new to Java 5.0. Versions of Java older than that will not work.

Chapter Topics:

• Review of fixed-length arrays
• The ArrayList class
  
• ArrayList constructors
  
• The List interface
  
• capacity and size
  
• Methods of ArrayList
  • add(),   clear()
  • get(),   indexOf()
  • isEmpty(),   remove(),   size()
• Iterators
  
• Autoboxing

Question 1:
(Review: ) Examine the following:
String[] list = new String[3];
What is the length of the array referenced by list?

Source: Bradley Kjell, http://programmedlessons.org/Java9/chap85/ch85_01.html
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 License.