It’s
a fairly simple program that has only a fixed quantity of objects with known
lifetimes.
In
general, your programs will always be creating new objects based on some
criteria that will be known only at the time the program is running. You
won’t know until run-time the quantity or even the exact type of the
objects you need. To solve the general programming problem, you need to create
any number of objects, anytime, anywhere. So you can’t rely on creating a
named handle to hold each one of your objects:
MyObject
myHandle;
since
you’ll never know how many of these things you’ll actually need.
To
solve this rather essential problem, Java has several ways to hold objects (or
rather, handles to objects). The built-in type is the array, which has been
discussed before and will get additional coverage in this chapter. Also, the
Java utilities library has some collection
classes
(also known as container
classes
,
but that term is used by the AWT so “collection” will be used here)
that provide more sophisticated ways to hold and even manipulate your objects.
This will comprise the remainder of this chapter.