Java4010: getting started with java collections

Revised: Tue Apr 05 13:19:04 CDT 2016

This page is included in the following Books:

• ITSE 2321 - Object-Oriented Programming (Java)
• Object-Oriented Programming (OOP) with Java

Table of contents

• Preface
  • Viewing tip
    • Listings
• Preview
• Generics
• Introduction
  • A quiz
  • Elements of the Framework are easy to use
  • Don't reinvent the wheel
  • Collections Framework encourages reuse
• Sample program
• Interesting code fragments
  • An object of the TreeSet class
  • Collection is an interface
  • What is a TreeSet object?
    • What does ascending element order mean?
    • What does log(n) time cost mean?
    • A TreeSet object is a Set
    • A TreeSet object is a SortedSet
    • A TreeSet object is a Collection
  • Populate the Collection
    • Don't know, don't care
    • Polymorphism in action
    • Add five elements with some duplicates
    • Filter out the duplicates
    • Notification of duplicates
    • Sort the elements
    • The TreeSet object is now populated
  • Get an Iterator object
    • Again, don't know, don't care
    • An Iterator object acts as a doorkeeper
    • Traverse the collection
    • Four elements with no duplicates
  • An editorial opinion
    • What kind of knowledge is needed?
    • The same concept applies to software design
    • An analogy
    • Its time to reinvent the CS2 curriculum
• Run the program
• Summary
• What's next?
• Miscellaneous
• Complete program listing

Preface

This module is one of a series of modules designed to teach you about Object-Oriented Programming in general and the Java Collectionsframework in particular.

The purpose of this module is to introduce you to the Java Collections Framework. Once you learn how to use the framework, it is unlikely that you will need to reinvent common data structures, search algorithms, or sorting algorithms again, because those capabilities are neatly packaged within the framework.

In addition to studying these modules, I strongly recommend that you study the Collections Trail in Oracle's Java Tutorials . The modules in this collection are intended to supplement and not to replace those tutorials.

Viewing tip

I recommend that you open another copy of this module in a separate browser window and use the following links to easily find and view the listings while you are reading about them.

Listings

• Listing 1 . A new object of the TreeSet class.
• Listing 2 . Populate the collection.
• Listing 3 . The Populator class.
• Listing 4 . Get an Iterator object.
• Listing 5 . Traverse the collection.
• Listing 6 . Complete program listing

Preview

This module provides a brief introduction to the use of the Java Collections Framework . The framework is designed to encourage you to reuse rather than to reinvent collections and maps.

A collection represents a group of objects, known as its elements. Some collections allow duplicate elements while others do not. Some collections areordered and others are not. (Maps will be discussed in future modules.)