The Java Course

By by Allen B. Downey

This edition of the eBook "Java Course" is based on the well-known book by Allen B. Downey, "How to Think Like a Computer Scientist". The main reason for rearranging the original material was to provide the book not only as a printable copy (i.e. as a PDF file) but also as an indexed and easy-to-navigate electronic book which is available both online and offline. In addition, we focused on enhancing the accessibility of the texts by improving the index, by splitting the chapters into managable (and readable) parts, and by adding lots of "see also" hints and cross links.

Finally, we decided to publish this eBook as an MS Windows HTML Help file offering the same navigation structure as the Web-based version. We hope that this service makes it easier for many beginners to learn how to program under Java.

Contents

• The way of the program
• What is a programming language?
• What is a program?
• What is debugging?
• Formal and natural languages
• The first program
• Java Variables and types
• More printingVariables
• Assignment
• Printing variables
• Keywords
• Operators
• Order of operations
• Operators for Strings
• Composition
• Java Methods
• Floating-point
• Converting from double to int
• Math methods
• Composition
• Adding new methods
• Classes and methods
• Programs with multiple methods
• Methods with results
• Java Conditionals, graphics and recursion
• The modulus operator
• Conditional execution
• Alternative execution
• Chained conditionals
• Nested conditionals
• The return statement
• Type conversion
• Slates and Graphics objects
• Invoking methods on a Graphics object
• Coordinates
• A lame Mickey Mouse
• Other drawing commands
• Recursion
• fractal Mickey Mouse
• Stack diagrams for recursive methods
• Convention and divine law
• Fruitful Java methods
• Return values
• Program development
• Composition
• Overloading
• Boolean expressions
• Logical operators
• Boolean methods
• More recursion
• Leap of faith
• One more example
• Java Iteration
• Multiple assignment
• Iteration
• The while statement
• Tables
• Two-dimensional tables
• Encapsulation and generalization
• Methods
• More encapsulation
• Local variables
• More generalization
• Java Strings and things
• Invoking methods on objects
• LengthTraversal
• Run-time errors
• Reading documentation
• The indexOf method
• Looping and counting
• Increment and decrement operators
• Character arithmetic
• Strings are immutable
• Strings are incomparable
• Java Interesting objects
• What's interesting?
• Packages
• Point objects
• Instance variables
• Objects as parameters
• Rectangles
• Objects as return types
• Objects are mutableAliasingnull
• Garbage collection
• Objects and primitives
• Create your own Java objects
• Class definitions and object types
• Time
• Constructors
• More constructors
• Creating a new object
• Printing an object
• Operations on objects
• Pure functions
• Modifiers
• Fill-in methods
• Which is best?
• Incremental development vs. planning
• Generalization
• Algorithms
• Arrays
• Arrays of Objects
• Objects of Arrays
• Object-oriented programming
• Linked lists
• Stacks
• Queues and Priority Queues
• Trees
• HeapTable
• Appendix
• Index

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JDK 1.4 Tutorial

The JDK 1.4 release of the Java programming language from Sun Microsystems represents a substantial step in Java’s progress. Some of the new features are packages that have been in use for some time but have not yet been part of the core Java platform; other features are completely new.

Whatever their origin, these features extend Java’s capabilities, encapsulating complex functionality behind simple abstractions. Some of the features help integrate Java further into the host operating system, providing direct access to services that had previously only been accessible to native code.

This book is decidedly code-centric. The central feature of each chapter is a program or set of programs that demonstrate the subject of the chapter within a complete, real-world program. Although each chapter starts with an overview of its topic and outlines the main classes and methods of the crucial packages, it does not duplicate information that can easily be found in the Java documentation.

Thus, this book should be considered a by-example companion to the comprehensive documentation. As you peruse the chapter descriptions that follow, you may notice that this book does not rigorously cover all topics. I consider a number of topics too broad to be covered in any useful way in a book of this kind; such topics generally need their own book. These include CORBA (including the new Portable Object Adapter (POA) Object Request Broker (ORB)), XML, the Java Cryptography Extension (JCE), and the Java Authentication and Authorization Service (JAAS).

At the time this book was being prepared, it did not seem possible to acquire a driver that supported enough JDBC 3.0 features to make testing possible. Rather than write from a position of ignorance, and include possibly spurious code listings, I decided not to include a chapter on this important topic.

Sadly, the Generics (parameterized types) feature was, in the end, not included with JDK 1.4 as originally promised. This controversial addition to the language looks like it will be included in JDK 1.5 for sure, and you can download an early-access version of it from Sun. However, since it requires a change to the compiler, it can’t really be said to be a part of JDK 1.4 and so is not discussed in this book.

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Sun Java Tutorials

The Java Tutorials are practical guides for programmers who want to use the Java programming language to create applications. They include hundreds of complete, working examples, and dozens of lessons. Groups of related lessons are organized into "trails".

• Getting Started — An introduction to Java technology and lessons on installing Java development software and using it to create a simple program.
• Learning the Java Language — Lessons describing the essential concepts and features of the Java Programming Language.
• Essential Java Classes — Lessons on exceptions, basic input/output, concurrency, regular expressions, and the platform environment.
• Collections — Lessons on using and extending the Java Collections Framework.
• Swing — An introduction to the Swing GUI toolkit, with an overview of features and a visual catalog of components. See below for a more comprehensive tutorial on Swing.
• Deployment — How to package applications and applets using JAR files, and deploy them using Java Web Start and Java Plug-in.
• Preparation for Java Programming Language Certification — List of available training and tutorial resources.

Specialized Trails and Lessons

These trails and lessons are only available as web pages.

• Custom Networking — An introduction to the Java platform's powerful networking features.
• The Extension Mechanism — How to make custom APIs available to all applications running on the Java platform.
• Full-Screen Exclusive Mode API — How to write applications that more fully utilize the user's graphics hardware.
• Generics — An enhancement to the type system that supports operations on objects of various types while providing compile-time type safety. Note that this lesson is for advanced users. The Java Language trail contains a Generics lesson that is suitable for beginners.
• Internationalization — An introduction to designing software so that it can be easily be adapted (localized) to various languages and regions.
• JavaBeans — The Java platform's component technology.
• JDBC Database Access — Introduces an API for connectivity between the Java applications and a wide range of databases and a data sources.
• JMX— Java Management Extensions provides a standard way of managing resources such as applications, devices, and services.
• JNDI— Java Naming and Directory Interface enables accessing the Naming and Directory Service such as DNS and LDAP.
• RMI — The Remote Method Invocation API allows allows an object to invoke methods of an object running on another Java Virtual Machine.
• Reflection — An API that represents ("reflects") the classes, interfaces, and objects in the current Java Virtual Machine.
• Security — Java platform features that help protect applications from malicious software.
• Sound — An API for playing sound data from applications.
• 2D Graphics — How to display and print 2D graphics in applications.

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