Introduction to Programming Using Java – David J. Eck

Introduction to Programming Using Java Version 5.0, December 2006
(Version 5.0.2, with minor corrections, November 2007)
David J. Eck

Introduction to Programming Using Java - David J. Eck

Introduction to Programming Using Java – David J. Eck

Hobart and William Smith Colleges
c 1996–2007, David J. Eck

David J. Eck (
Department of Mathematics and Computer Science
Hobart and William Smith Colleges
Geneva, NY 14456

This book can be distributed in unmodified form with no restrictions. Modified versions can be made and distributed provided they are distributed under the same license as the original. More specifically: This work is licensed under the Creative Commons Attribution-Share Alike 2.5 License. To view a copy of this license, visit sa/2.5/ or send a letter to Creative Commons, 543 Howard Street, 5th Floor, San Francisco, California, 94105, USA.
The web site for this book is:


Preface xiii

1. The Mental Landscape

1.1. Machine Language
1.2. Asynchronous Events
1.3 The Java Virtual Machine
1.4 Building Blocks of Programs
1.5 Object-oriented Programming
1.6 The Modern User Interface
1.7 The Internet
Quiz on Chapter

2. Names and Things

2.1 The Basic Java Application
2.2 Variables and Types
2.2.1 Variables
2.2.2 Types and Literals
2.2.3 Variables in Programs

2.3 Objects and Subroutines

2.3.1 Built-in Subroutines and Functions
2.3.2 Operations on Strings
2.3.3 Introduction to Enums

2.4 Text Input and Output

2.4.1 A First Text Input Example
2.4.2 Text Output
2.4.3 TextIO Input Functions
2.4.4 Formatted Output
2.4.5 Introduction to File I/O

2.5 Details of Expressions

2.5.1 Arithmetic Operators
2.5.2 Increment and Decrement
2.5.3 Relational Operators
2.5.4 Boolean Operators
2.5.5 Conditional Operator
2.5.6 Assignment Operators and Type-Casts
2.5.7 Type Conversion of Strings
2.5.8 Precedence Rules

2.6 Programming Environments

2.6.1 Java Development Kit
2.6.2 Command Line Environment
2.6.3 IDEs and Eclipse
2.6.4 The Problem of Packages
Exercises And Quiz for Chapter 2

Java programming 7 Introduction to Programming Using Java - David J. Eck

3. Control

3.1 Blocks, Loops, and Branches
3.1.1 Blocks
3.1.2 The Basic While Loop
3.1.3 The Basic If Statement

3.2 Algorithm Development

3.2.1 Pseudocode and Stepwise Refinement
3.2.2 The 3N+1 Problem
3.2.3 Coding, Testing, Debugging

3.3 while and do..while

3.3.1 The while Statement
3.3.2 The do..while Statement
3.3.3 break and continue

3.4 The for Statement

3.4.1 For Loops
3.4.2 Example: Counting Divisors
3.4.3 Nested for Loops
3.4.4 Enums and for-each Loops

3.5 The if Statement

3.5.1 The Dangling else Problem
3.5.2 The if…else if Construction
3.5.3 If Statement Examples
3.5.4 The Empty Statement

3.6 The switch Statement

3.6.1 The Basic switch Statement
3.6.2 Menus and switch Statements
3.6.3 Enums in switch Statements
3.6.4 Definite Assignment

3.7 Exceptions and try..catch

3.7.1 Exceptions
3.7.2 try..catch
3.7.3 Exceptions in TextIO
3.8 GUI Programming

Exercises for Chapter 3
Quiz on Chapter 3

Java programming 2 Introduction to Programming Using Java - David J. Eck

4. Subroutines

4.1. Black Boxes

4.2. Static Subroutines and Variables

4.2.1 Subroutine Definitions
4.2.2 Calling Subroutines

4.2.3 Subroutines in Programs
4.2.4 Member Variables

4.3. Parameters

4.3.1 Using Parameters
4.3.2 Formal and Actual Parameters
4.3.3 Overloading
4.3.4 Subroutine Examples
4.3.5 Throwing Exceptions
4.3.6 Global and Local Variables

4.4 Return Values

4.4.1 The return statement
4.4.2 Function Examples
4.4.3 3N+1 Revisited

4.5 APIs, Packages, and Javadoc

4.5.1 Toolboxes
4.5.2 Java’s Standard Packages
4.5.3 Using Classes from Packages
4.5.4 Javadoc

4.6. More on Program Design

4.6.1 Preconditions and Postconditions
4.6.2 A Design Example
4.6.3 The Program

4.7. The Truth About Declarations

4.7.1 Initialization in Declarations
4.7.2 Named Constants
4.7.3 Naming and Scope Rules

Exercises for Chapter 4
Quiz on Chapter 4

Java programming 5 Introduction to Programming Using Java - David J. Eck

5. Objects and Classes

5.1. Objects and Instance Methods

5.1.1. Objects, Classes, and Instances
5.1.2. Fundamentals of Objects
5.1.3. Getters and Setters

5.2. Constructors and Object Initialization

5.2.1. Initializing Instance Variables
5.2.2. Constructors
5.2.3. Garbage Collection

5.3. Programming with Objects

5.3.1. Some Built-in Classes
5.3.2. Wrapper Classes and Autoboxing
5.3.3. The class “Object”
5.3.4. Object-oriented Analysis and Design

5.4. Programming Example: Card, Hand, Deck

5.4.1. Designing the classes
5.4.2. The Card Class
5.4.3. Example: A Simple Card Game

5.5. Inheritance and Polymorphism

5.5.1. Extending Existing Classes
5.5.2. Inheritance and Class Hierarchy
5.5.3. Example: Vehicles
5.5.4. Polymorphism
5.5.5. Abstract Classes

5.6. this and super

5.6.1. The Special Variable this
5.6.2. The Special Variable super
5.6.3 Constructors in Subclasses

5.7. Interfaces

5.7.1. Defining and Implementing Interfaces
5.7.2. Interfaces as Types
5.7.3. Interfaces in Java 8

5.8 Nested Classes

5.8.1. Static Nested Classes
5.8.2. Inner Classes
5.8.3. Anonymous Inner Classes
5.8.4. Java 8 Lambda Expressions

Exercises for Chapter 5
Quiz on Chapter 5

Java programming 3 Introduction to Programming Using Java - David J. Eck

6 Introduction to GUI Programming

6.1 The Basic GUI Application

6.1.1 JFrame and JPanel
6.1.2 Components and Layout
6.1.3 Events and Listeners
6.1.4 Some Java GUI History

6.2 Applets and HTML

6.2.1 JApplet
6.2.2 Reusing Your JPanels
6.2.3 Basic HTML

6.2.4 Applets on Web Pages

6.3 Graphics and Painting

6.3.1 Coordinates
6.3.2 Colors
6.3.3 Fonts
6.3.4 Shapes
6.3.5 Graphics2D
6.3.6 An Example

6.4 Mouse Events

6.4.1 Event Handling
6.4.2 MouseEvent and MouseListener
6.4.3 Mouse Coordinates
6.4.4 MouseMotionListeners and Dragging
6.4.5 Anonymous Event Handlers

6.5 Timer and Keyboard Events

6.5.1 Timers and Animation
6.5.2 Keyboard Events
6.5.3 Focus Events
6.5.4 State Machines

6.6 Basic Components

6.6.1 JButton
6.6.2 JLabel
6.6.3 JCheckBox
6.6.4 JTextField and JTextArea
6.6.5 JComboBox
6.6.6 JSlider
6.7 Basic Layout
6.7.1 Basic Layout Managers
6.7.2 Borders
6.7.3 Slider And Combo Box Demo
6.7.4 A Simple Calculator
6.7.5 Using a null Layout
6.7.6 A Little Card Game

6.8 Menus and Dialogs

6.8.1 Menus and Menubars
6.8.2 Dialogs
6.8.3 Fine Points of Frames
6.8.4 Creating Jar Files

Exercises for Chapter 6
Quiz on Chapter 6

Java programming 5 Introduction to Programming Using Java - David J. Eck

7. Arrays

7.1 Creating and Using Arrays

7.1.1 Arrays
7.1.2 Using Arrays
7.1.3 Array Initialization

7.2 Programming With Arrays

7.2.1 Arrays and for Loops
7.2.2 Arrays and for-each Loops
7.2.3 Array Types in Subroutines
7.2.4 Random Access
7.2.5 Arrays of Objects
7.2.6 Variable Arity Methods

7.3 Dynamic Arrays and ArrayLists

7.3.1 Partially Full Arrays
7.3.2 Dynamic Arrays
7.3.3 ArrrayLists
7.3.4 Parameterized Types
7.3.5 Vectors

7.4 Searching and Sorting

7.4.1 Searching
7.4.2 Association Lists
7.4.3 Insertion Sort
7.4.4 Selection Sort
7.4.5 Unsorting

7.5 Multi-dimensional Arrays

7.5.1 Creating Two-dimensional Arrays
7.5.2 Using Two-dimensional Arrays
7.5.3 Example: Checkers

Exercises for Chapter 7
Quiz on Chapter 7

Java programming 7 Introduction to Programming Using Java - David J. Eck

8. Correctness and Robustness

8.1 Introduction to Correctness and Robustness

8.1.1 Horror Stories
8.1.2 Java to the Rescue
8.1.3 Problems Remain in Java

8.2 Writing Correct Programs

8.2.1 Provably Correct Programs
8.2.2 Robust Handling of Input

8.3 Exceptions and try..catch

8.3.1 Exceptions and Exception Classes
8.3.2 The try Statement
8.3.3 Throwing Exceptions
8.3.4 Mandatory Exception Handling
8.3.5 Programming with Exceptions

8.4 Assertions

8.5 Introduction to Threads

8.5.1 Creating and Running Threads
8.5.2 Operations on Threads
8.5.3 Mutual Exclusion with “synchronized”
8.5.4 Wait and Notify
8.5.5 Volatile Variables
8.6 Analysis of Algorithms

Exercises for Chapter 8
Quiz on Chapter 8

Java programming 8 Introduction to Programming Using Java - David J. Eck

9. Linked Data Structures and Recursion

9.1 Recursion

9.1.1 Recursive Binary Search
9.1.2 Towers of Hanoi
9.1.3 A Recursive Sorting Algorithm
9.1.4 Blob Counting

9.2 Linked Data Structures

9.2.1 Recursive Linking
9.2.2 Linked Lists
9.2.3 Basic Linked List Processing
9.2.4 Inserting into a Linked List
9.2.5 Deleting from a Linked List

9.3 Stacks, Queues, and ADTs

9.3.1 Stacks
9.3.2 Queues
9.3.3 Postfix Expressions

9.4. Binary Trees

9.4.1 Tree Traversal
9.4.2 Binary Sort Trees
9.4.3 Expression Trees

9.5. A Simple Recursive Descent Parser

9.5.1 Backus-Naur Form
9.5.2 Recursive Descent Parsing
9.5.3 Building an Expression Tree

Exercises for Chapter 9
Quiz on Chapter 9

Java programming 9 Introduction to Programming Using Java - David J. Eck

10. Generic Programming and Collection Classes

10.1 Generic Programming

10.1.1 Generic Programming in Smalltalk
10.1.2 Generic Programming in C++
10.1.3 Generic Programming in Java
10.1.4 The Java Collection Framework
10.1.5 Iterators and for-each Loops
10.1.6 Equality and Comparison
10.1.7 Generics and Wrapper Classes

10.2. Lists and Sets

10.2.1 ArrayList and LinkedList
10.2.2 Sorting
10.2.3 TreeSet and HashSet
10.2.4 EnumSet

10.3. Maps

10.3.1. The Map Interface
10.3.2. Views, SubSets, and SubMaps
10.3.3. Hash Tables and Hash Codes

10.4. Programming with the Collection Framework

10.4.1. Symbol Tables
10.4.2. Sets Inside a Map
10.4.3. Using a Comparator
10.4.4. Word Counting

10.5. Writing Generic Classes and Methods

10.5.1. Simple Generic Classes
10.5.2. Simple Generic Methods
10.5.3. Type Wildcards
10.5.4. Bounded Types

Exercises for Chapter 10
Quiz on Chapter 10

Java programming 10 Introduction to Programming Using Java - David J. Eck

11. Files and Networking

11.1. Streams, Readers, and Writers

11.1.1. Character and Byte Streams
11.1.2. PrintWriter
11.1.3. Data Streams
11.1.4. Reading Text

11.1.5. The Scanner Class
11.1.6. Serialized Object I/O

11.2. Files

11.2.1. Reading and Writing Files
11.2.2. Files and Directories
11.2.3. File Dialog Boxes

11.3. Programming With Files

11.3.1. Copying a File
11.3.2. Persistent Data
11.3.3. Files in GUI Programs
11.3.4. Storing Objects in Files

11.4. Networking

11.4.1. URLs and URLConnections
11.4.2. TCP/IP and Client/Server
11.4.3. Sockets
11.4.4. A Trivial Client/Server
11.4.5. A Simple Network Chat

11.5. Network Programming and Threads

11.5.1. A Threaded GUI Chat Program.
11.5.2. A Multithreaded Server
11.5.3. Distributed Computing
11.6. A Brief Introduction to XML
11.6.1. Basic XML Syntax
11.6.2. XMLEncoder and XMLDecoder
11.6.3. Working With the DOM

Exercises for Chapter 11
Quiz on Chapter 11

Java programming 6 Introduction to Programming Using Java - David J. Eck

12. Advanced GUI Programming

12.1. Images and Resources

12.1.1. Images and BufferedImages
12.1.2. Working With Pixels
12.1.3. Resources
12.1.4. Cursors and Icons
12.1.5. Image File I/O

12.2. Fancier Graphics

12.2.1. Measuring Text
12.2.2. Transparency
12.2.3. Antialiasing
12.2.4. Strokes and Paints
12.2.5. Transforms

12.3. Actions and Buttons

12.3.1. Action and AbstractAction
12.3.2. Icons on Buttons
12.3.3. Radio Buttons
12.3.4. Toolbars
12.3.5. Keyboard Accelerators
12.3.6. HTML on Buttons

12.4. Complex Components and MVC

12.4.1. Model-View-Controller
12.4.2. Lists and ListModels
12.4.3. Tables and TableModels
12.4.4. Documents and Editors
12.4.5. Custom Components

12.5. Finishing Touches

12.5.1. The Mandelbrot Set
12.5.2. Design of the Program
12.5.3. Internationalization
12.5.4. Events, Events, Events
12.5.5. Custom Dialogs
12.5.6. Preferences

Exercises for Chapter 12
Quiz on Chapter 12



Introduction to Programming Using Java is a free introductory computer programming textbook that uses Java as the language of instruction. It is suitable for use in an introductory programming course and for people who are trying to learn programming on their own. There are no prerequisites beyond a general familiarity with the ideas of computers and programs. There is enough material for a full year of college-level programming. Chapters 1 through 7 can be used as a textbook in a one-semester college-level course or in a year-long high school course.

This version of the book covers “Java 5.0”, and many of the examples use features that were not present in earlier versions of Java. (Sometimes, you will see this version of Java referred to as Java 1.5 instead of Java 5.0.) Note that Java applets appear throughout the pages of the on-line version of this book. Many of those applets will be non-functional in Web browsers that do not support Java 5.0.

The home web site for this book is The page at that address contains links for downloading a copy of the web site and for downloading a PDF version of the book.

∗ ∗ ∗

In style, this is a textbook rather than a tutorial. That is, it concentrates on explaining concepts rather than giving step-by-step how-to-do-it guides. I have tried to use a conversational writing style that might be closer to classroom lecture than to a typical textbook. You’ll find programming exercises at the end of most chapters, and you will find a detailed solution for each exercise, with the sort of discussion that

I would give if I presented the solution in class. (Solutions to the exercises can be found in the on-line version only.) I strongly advise that you read the exercise solutions if you want to get the most out of this book. This is certainly not a Java reference book, and it is not even close to a comprehensive survey of all the features of Java. It is not written as a quick introduction to Java for people who already know another programming language.

Instead, it is directed mainly towards people who are learning programming for the first time, and it is as much about general programming concepts as it is about Java in particular. I believe that Introduction to Programming using Java is fully competitive with the conventionally published, printed programming textbooks that are available on the market. (Well, all right, I’ll confess that I think it’s better.)

There are several approaches to teaching Java. One approach uses graphical user interface programming from the very beginning. Some people believe that object oriented programming should also be emphasized from the very beginning. This is not the approach that I take. The approach that I favor starts with the more basic building blocks of programming and builds from there.

After an introductory chapter, I cover procedural programming in Chapters 2, 3, and 4. Object-oriented programming is introduced in Chapter 5. Chapters 6 covers the closely related topic of event-oriented programming and graphical user interfaces. Arrays are covered in Chapter 7. Chapter 8 marks a turning point in the book, moving beyond the fundamental ideas of programming to cover more advanced topics. Chapter 8 is mostly about writing robust and correct programs, but it also has a section on parallel processing and threads.

Chapters 9 and 10 cover recursion and data structures, including the Java Collection Framework. Chapter 11 is about files and networking. Finally, Chapter 12 returns to the topic of graphical user interface programming to cover some of Java’s more advanced capabilities.

∗ ∗ ∗

Major changes have been made in the fifth edition. Perhaps the most significant change is the use of parameterized types in the chapter on generic programming. Parameterized types— Java’s version of templates—were the most eagerly anticipated new feature in Java 5.0.

Other new features in Java 5.0 are also covered. Enumerated types are introduced, although they are not covered in their full complexity. The “for-each” loop is covered and is used extensively. Formatted output is also used extensively, and the Scanner class is covered (though not until Chapter 11). Static import is covered briefly, as are variable arity methods.

The non-standard TextIO class that I use for input in the first half of the book has been rewritten to support formatted output. I have also added some file I/O capabilities to this class to make it possible to cover some examples that use files early in the book.

Javadoc comments are covered for the first time in this edition. Almost all code examples have been revised to use Javadoc-style comments.

The coverage of graphical user interface programming has been reorganized, much of it has been rewritten, and new material has been added. In previous editions, I emphasized applets. Stand-alone GUI applications were covered at the end, almost as an afterthought.

In the fifth edition, the emphasis on applets is gone, and almost all examples are presented as stand-alone applications. However, applet versions of each example are still presented on the web pages of the on-line version of the book. The chapter on advanced GUI programming has been moved to the end, and a significant amount of new material has been added, including coverage of some of the features of Graphics2D.

Aside from the changes in content, the appearance of the book has been improved, especially the appearance of the PDF version. For the first time, the quality of the PDF approaches that of conventional textbooks.

∗ ∗ ∗

The latest complete edition of Introduction to Programming using Java is always available on line at The first version of the book was written in 1996, and there have been several editions since then. All editions are archived at the following Web addresses:

First edition: (Covers Java 1.0.)

Second edition: (Covers Java 1.1.)

Third edition: (Covers Java 1.1.)

Fourth edition: (Covers Java 1.4.)

Fifth edition: (Covers Java 5.0.)

Introduction to Programming using Java is free, but it is not in the public domain. As of Version 5.0, it is published under the terms of the Creative Commons Attribution-Share Alike 2.5 License. To view a copy of this license, visit or send a letter to Creative Commons, 543 Howard Street, 5th Floor, San Francisco, California, 94105, USA. This license allows redistribution and modification under certain terms. For example, you can:

Post an unmodified copy of the on-line version on your own Web site (including the parts that list the author and state the license under which it is distributed!).

Give away or sell printed, unmodified copies of this book, as long as they meet the re-quirements of the license.

Make modified copies of the complete book or parts of it and post them on the web or otherwise distribute them, provided that attribution to the author is given, the modifica-tions are clearly noted, and the modified copies are distributed under the same license as the original. This includes translations to other languages.

While it is not actually required by the license, I do appreciate hearing from people who are using or distributing my work.

∗ ∗ ∗

A technical note on production: The on-line and PDF versions of this book are created from a single source, which is written largely in XML. To produce the PDF version, the XML is processed into a form that can be used by the TeX typesetting program. In addition to XML files, the source includes DTDs, XSLT transformations, Java source code files, image files, a TeX macro file, and a couple of scripts that are used in processing.

I have not made the source materials available for download, since they are not in a clean enough form to be publishable, and because it would require a fair amount of expertise to make any use of them. However, they are not meant to be secret, and I am willing to make them available on request.
∗ ∗ ∗

Professor David J. Eck

Department of Mathematics and Computer Science

Hobart and William Smith Colleges

Geneva, New York 14456, USA



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