Ivor Horton's Beginning Java™ 2, JDK™ 5th Edition

14.1. Understanding the Collections Framework

The Java collections framework is a set of generic types that you use to create collection classes that support various ways for you to store and manage objects of any kind in memory. As I'm sure you appreciate from the previous chapter, a collection class is simply a class that organizes a set of objects of a given type in a particular way, such as in a linked list or a pushdown stack. The majority of types that make up the collections framework are defined in the java.util package.

Using a generic type for your collections of objects means that you get static checking by the compiler for whatever types of objects you want to manage. This ensures that you do not inadvertently attempt to store objects of the wrong type in a collection. The collections framework includes a professional implementation of a generic type that implements a linked list, which is vastly superior to the linked list that you took so much trouble to develop for yourself first as an ordinary class back in Chapter 6, and later as a generic type in Chapter 13. However, the effort wasn't entirely wasted as you now have a good idea of how linked lists work and how generic types are defined.

You'll find that the collections framework is a major asset in most of your programs. When you want an array that automatically expands to accommodate however many objects you throw into it, or you need to be able to store and retrieve an object based on what it is rather than ...