The ArrayList Class in Java

The ArrayList Class in Java
An Introduction

Prof. David Bernstein
James Madison University

Computer Science Department

bernstdh@jmu.edu

Review

An Array:
- A fixed-size "group" of homogeneous objects each of which is identified by an integer index
Limitations of Arrays:
- Fixed size

The java.util.ArrayList Class

Type-Safety and Collections

Elements in a Collection:
- In Java, one can put Object objects in a collection
- Effectively, this means that you can put any reference type in a collection
A Shortcoming of this Approach:
- You are forced to cast the Object to the appropriate type when you retrieve it
- You may cast it incorrectly and this mistake will only be caught at run-time
Overcoming this Shortcoming:
- Use parameterized classes/interfaces

A Type-Safe ArrayList

What About Primitive Types?

The Declarations:
- ArrayList<Boolean>
- ArrayList<Double>
- ArrayList<Integer>
Why/How This Works:
- This is a topic for another lecture