CS 110: Introduction to Computer Science Spring 2008
Arrays, Collections, and the class Object
In this lesson, we’ll learn more about built-in arrays, ArrayList,
and Java library classes in general. To do this, we’ll talk about
how the ArrayList class in the Java library is implemented.
IntArray implementation
ArrayList is a class that 'wraps' Java's built-in array, providing a
list that can grow. It is generic, in that one can use ArrayList for a
list with elements of any type.
We’ll begin with an IntArray class that wraps a built-in integer
array.
Instructor coding: Write an IntArray class with append and get:
1. Define a built-in array as a ‘private’ data member
2. Define an additional data member: the number of elements.
3. Write the methods ‘add’, ‘get’, and ‘toString’
4. Write a main which tests these functions
Our IntArray is limited, relative to ArrayList.
It doesn’t grow as needed
It is type-specific
To make it grow as needed, we’ll need to modify the ‘add’
method:
If we’ve reached the size limit of the array:
1. create a new array of twice the size
2. copy the old data to the new array
3. point the data member of intArray to the new array
