COMPUTERS GET A LOT OF THEIR POWER from working with
data structures. A data structure is an organized
collection of related data. An object is a data structure, but
this type of data structure -- consisting of a fairly small number of named
instance variables -- is just the beginning.
In many cases, programmers build complicated data
structures by hand, by linking objects together. We'll look at these
custom-built data structures in Chapter 11. But there is one type of data
structure that is so important and so basic that it is built into every
programming language: the array.
An array is a data
structure consisting of a numbered list of items, where all the items
are of the same type. In Java, the items in an array are always numbered
from zero up to some maximum value, which is set when the array is created.
For example, an array might
contain 100 integers, numbered from zero to 99. The items in an array
can belong to one of Java's primitive types. They can also be references to
objects, so that you could, for example, make an array containing
all the components in an applet.
This chapter discusses how arrays are created and used in Java.
It also covers the standard class java.util.ArrayList. An object of
type ArrayList is very similar to an array of Objects, but it can
grow to hold any number of items.
Contents of Chapter 8: