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Practical Java Programming Language Guide

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Practical Java Programming Language Guide


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  • Copyright 2000
  • Dimensions: 7-3/8" x 9-1/4"
  • Pages: 312
  • Edition: 1st
  • Book
  • ISBN-10: 0-201-61646-7
  • ISBN-13: 978-0-201-61646-0

This book does for Java what Scott Meyers' classic Effective C++ did for C++: identifies the key practices and rules that enable good developers to become great developers. IBM Java expert Peter Haggar brings together 68 rules for writing better Java 2 code, complete with insightful discussions and real-world examples. These are the "rules of thumb" expert developers have discovered: guidelines that consistently lead to clear, correct, and efficient code. Haggar focuses on the key issues virtually every Java developer faces, from general techniques (such as when to use polymorphism and when not to use method overloading); to working with objects, exception handling, performance, multithreading, classes, interfaces, and beyond. Haggar has a remarkable talent for crystallizing a problem and solution, and communicating it in words and code. The result: a book that can help any Java developer get dramatically better results -- fast.


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Table of Contents




Praxis 1: Understand that parameters are passed by value, not by reference.
Praxis 2: Use final for constant data and constant object references.
Praxis 3: Understand that all non-static methods can be overridden by default.
Praxis 4: Choose carefully between arrays and Vectors.
Praxis 5: Prefer polymorphism to instance of.
Praxis 6: Use instance of only when you must.
Praxis 7: Set object references to null when they are no longer needed.


Praxis 8: Differentiate between reference and primitive types.
Praxis 9: Differentiate between == and equals.
Praxis 10: Do not rely on the default implementation of equals.
Praxis 11: Implement the equals method judiciously.
Praxis 12: Prefer get Class in equals method implementations.
Praxis 13: Call super. equals of base classes.
Praxis 14: Consider carefully instance of in equals method implementations.
Praxis 15: Follow these rules when implementing an equals method.


Praxis 16: Know the mechanics of exception control flow.
Praxis 17: Never ignore an exception.
Praxis 18: Never hide an exception.
Praxis 19: Consider the drawback to the throws clause.
Praxis 20: Be specific and comprehensive with the throws clause.
Praxis 21: Use finally to avoid resource leaks.
Praxis 22: Do not return from a try block.
Praxis 23: Place try/catch blocks outside of loops.
Praxis 24: Do not use exceptions for control flow.
Praxis 25: Do not use exceptions for every error condition.
Praxis 26: Throw exceptions from constructors.
Praxis 27: Return objects to a valid state before throwing an exception.


Praxis 28: Focus initially on design, data structures, and algorithms.
Praxis 29: Do not rely on compile-time code optimization.
Praxis 30: Understand runtime code optimization.
Praxis 31: Use String Buffer, rather than String, for concatenation.
Praxis 32: Minimize the cost of object creation.
Praxis 33: Guard against unused objects.
Praxis 34: Minimize synchronization.
Praxis 35: Use stack variables whenever possible.
Praxis 36: Use static, final, and private methods to allow in lining.
Praxis 37: Initialize instance variables only once.
Praxis 38: Use primitive types for faster and smaller code.
Praxis 39: Do not use an Enumeration or an Iterator to traverse a Vector.
Praxis 40: Use System array copy for copying arrays.
Praxis 41: Prefer an array to a Vector or Array List.
Praxis 42: Reuse objects whenever possible.
Praxis 43: Use lazy evaluation.
Praxis 44: Optimize source code by hand.
Praxis 45: Compile to native code.


Praxis 46: Understand that for instance methods, synchronized locks objects, not methods or code.
Praxis 47: Distinguish between synchronized statics and synchronized instance methods.
Praxis 48: Use private data with an accessor method instead of public or protected data.
Praxis 49: Avoid unnecessary synchronization.
Praxis 50: Use synchronized or volatile when accessing shared variables.
Praxis 51: Lock all objects involved in a single operation.
Praxis 52: Acquire multiple locks in a fixed, global order to avoid deadlock.
Praxis 53: Prefer notify All to notify.
Praxis 54: Use spin locks for wait and notify All.
Praxis 55: Use wait and notify All instead of polling loops.
Praxis 56: Do not reassign the object reference of a locked object.
Praxis 57: Do not invoke the stop or suspend methods.
Praxis 58: Terminate threads through thread cooperation. Classes and Interfaces.
Praxis 59: Use interfaces to support multiple inheritance.
Praxis 60: Avoid method clashes in interfaces.
Praxis 61: Use abstract classes when it makes sense to provide a partial implementation.
Praxis 62: Differentiate between an interface, abstract class, and concrete class.
Praxis 63: Define and implement immutable classes judiciously.
Praxis 64: Use clone for immutable objects when passing or receiving object references to mutable objects.
Praxis 65: Use inheritance or delegation to define immutable classes.
Praxis 66: Call super. clone when implementing a clone method.
Praxis 67: Do not rely on finalize methods for non-memory resource cleanup.
Praxis 68: Use care when calling non-final methods from constructors.
Appendix: Learning Java.
Further Reading.
Colophon. 0201616467T04062001


This book is a collection of practical suggestions, advice, examples, and discussion about programming in the Java language. It is organized into individual lessons, each called a Praxis (pronounced prak-sis) and each discussing a particular topic. Each Praxis is written so that it stands on its own. You can read the book from front to back or select topics individually. This arrangement allows you to read the book in short intervals. Many Praxes (pronounced prak-sees) are fewer than five pages, thereby allowing you to study them in a brief amount of time.

In the book, I examine in detail particular design and programming issues. I chose the topics based on their relevancy to effective and efficient programming practices. One of the biggest complaints about Java is performance, so I devote the largest section of the book to this topic, exploring techniques to make Java code execute more efficiently.

I wrote this book as a guide to help you design and write code. It helps you understand Java more completely and enables you to write more-efficient, more-robust, and perhaps most important, more-correct code.

All of the information in this book applies to your Java programming. It is not particular to server, client, or GUI (graphical user interface) programming. In addition, you can apply this information to all versions and releases of Java.

The book's style was influenced by Scott Meyers' Effective C++ and More Effective C++ books. Because I found his style so useful as a way to organize a book, I decided to adopt a similar format.

Target Audience

This book is intended for Java programmers who already have grasped the basics of the language. It assumes the reader has a working knowledge of Java and concurrent programming and understands object-oriented concepts and terms. It is for the programmer who wants practical advice, discussion, and examples for using the language effectively.

This book provides seasoned Java programmers as well as programmers new to the language with information and discussion regarding key areas of Java. Enough new information is presented that experienced programmers will greatly benefit and be rewarded by looking at areas that they already know. For example, in some cases I discuss a familiar topic in a way that can help a programmer think about it differently or see another side to it not previously explored.

Programmers new to Java can also gain a lot from this book. I offer discussions and examples that help eliminate many common programming errors. I also dispel some common misconceptions about Java and highlight certain questions about specific language features.

Organization of This Book

This book is organized into six main sections.

  1. General Techniques--Presents several fundamental areas of Java programming including parameter passing, arrays, Vectors, and garbage collection.
  2. Objects and Equality--Examines objects and primitive types and how and why you should implement an equals method for a class.
  3. Exception Handling--Gives a detailed analysis of exception handling techniques and how to incorporate exceptions into your code effectively.
  4. Performance--Shows many techniques that you can use to improve the performance of your code. The JVM (Java Virtual Machine), bytecode, and JITs (Just-in-Time code generators) are examined.
  5. Multithreading--Covers aspects of the threading model that are critical to building robust and reliable multithreaded programs.
  6. Classes and Interfaces--Explains interfaces and abstract and concrete classes and where and when to use each. It also discusses immutable objects, cloning, and finalization in detail.

Under each of these headings is a varied number of related topics. Often, I discuss individual attributes of particular topics in more than one place. For example, I discuss the synchronized keyword at length but in various places. Each discussion deals with a different aspect of synchronized. However, I have provided extensive cross-referencing so that you will know, when reading a particular topic, where other relevant information exists.

Following the Contents is a Detailed Contents. This section contains all of the praxes headings and their page numbers, with a brief summary of the core instruction contained in each Praxis. You can use this Detailed Contents to refresh your memory about a topic or to locate a particular topic or subject matter.

The Appendix contains a proven technique to further expand your knowledge about Java. Also included is a Further Reading section, which lists relevant books and periodicals relating to Java and general design and programming.

A Few Words on the Word Praxis

Praxis is the result of my search for a word that summarizes what I am trying to do in this book. In the 1982 American Heritage Dictionary, Praxis is defined as follows: The practical application or exercise of a branch of learning. This is exactly what I want to do in the book.

The most appropriate definition is provided by Webster's New Collegiate Dictionary, 1958: Practice, especially of an art, science, or technical occupation; opposite to theory. This definition most accurately sums up what the book is about. The phrase, "opposite to theory," was the clincher. There is nothing wrong with theory. Its place, however, is not in this book.

Example Code

All code examples in the text have been compiled and run with the latest version of Java available when the book was written. The code was compiled and run with the Sun Java 2 SDK, Standard Edition, v1.2.1 on Windows NT 4.0. To access the source code, you must register the book at the following World Wide Web site:


At this Web site, you will need to enter the unique code found at the back of this book on the page entitled, "How to Register Your Book."

Providing Feedback

I welcome feedback on this book. Any comments, criticisms, or bug reports should be sent to PracticalJava@awl.com.

I hope you find this book useful, enjoyable, and practical.

Peter Haggar
Research Triangle Park, North Carolina
November, 1999




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