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One of the most important features of the Java language is support for multithreaded (also called concurrent) programming. This tutorial introduces you to the proper use of multiple threads in a Java program, using sample programs to illustrate these concepts. Before taking this course, you should have a general knowledge of Java programming; the context and level of knowledge used in this tutorial is the equivalent of an undergraduate operating systems course.

Glass box extensibility refers to the ways in which a software system may be extended when the source code is available for viewing, but not for modifying -- it lies as the happy medium between black box design (in which extensions are built without viewing the original code) and open box design (extensions are coded directly into the base code). Because the new extensions are based directly on the original code but don't alter it, the glass box design is probably the most effective, and safest, method of extending a software system. This article expands on the topic of glass box extensibility touched on last month in this column. After reading this article, you'll know when to use the glass box and will have some tips on how to implement it.

A core requirement of any non-trivial P2P application is secure communication between peers. While the details of the security depend on how the application will be used and on what it will protect, it's often possible to implement strong, general-purpose security using off-the-shelf technology such as SSL. This article demonstrates how to use SSL (via JSSE) in P2P security.

Java Web Start, a new technology to assist the development of client-side Java applications, is unique in that it frees you from concerning yourself with how the client is launched, either from a Web browser or from the desktop. Additionally, this technology provides an encompassing deployment scheme that enables a Web server to independently distribute and update client code. This article introduces this enterprising new technology, which is scheduled to be integrated in the final release of Java 1.4, describing its implementation from both the developer and the user perspective.

The addition of the java.util.prefs package to Java 1.4 (through JSR 10) lets you manipulate user preference data and configuration data by providing you with access to an implementation-specific registry (for example, the Windows Registry on Windows platforms). This article introduces you to the Preferences class and walks you through its use. It puts it all together with a sample program.

One of the strengths of the Java platform is its object-oriented nature; one of the benefits of object-oriented languages is that they aid code reuse. But what if you're a Java programmer and you want to reuse code that wasn't written in the Java language? With Bridge2Java, an IBM alphaWorks technology, Java developers can integrate COM objects into their applications. This article explains how it works.

Why invent the wheel every time you develop an application in Java? Writing a J2EE web application is complicated enough; you would not write a linked list module in C++ every time you started a new project. You would rather use another person's implementation. The same reuse-idea surely applies to server-side web development. This article looks at the best practices of using one popular web application toolkit, Expresso Framework. The idea of using custom tags, JSP, and the MVC paradigm are suitable for such frameworks. It will illustrate the best of practice through an on-line stock trading program example.

Project Jxta is a community-run attempt to build a utility application substrate for peer-to-peer applications. The initial reference implementation of Jxta includes a command-line shell that allows experimentation with the core Jxta platform without programming. This article takes us through a hands-on tour of the <a href="http://www-106.ibm.com/developerworks/java/library/j-p2pint2?open&l=766,t=grj,p=Jxta2">Jxta shell</a>. You'll explore its command set and extend its capability by writing your own custom commands using the Java programming language.

While it's common to hear that synchronized method calls can be 50 times as expensive as unsynchronized method calls, these numbers can actually be quite misleading. With each successive JVM version, overall performance has improved, and the cost of uncontended synchronization has been reduced, making the issue of uncontended synchronization overhead less significant. Contended synchronization, however, is quite expensive. Moreover, a high degree of contention is disastrous for scalability -- an application that had a high degree of contended synchronization will exhibit markedly worse performance as the load increases. This article explores several techniques for reducing contention, and hence improving scalability, in your programs.

This tutorial provides an overview of the Java Message Service (JMS) and offers the basics for developing programs that use it. JMS provides a way for Java programs to access an enterprise messaging system, also known as message oriented middleware (MOM). MOM provides a mechanism for integrating applications in a loosely coupled, flexible manner by providing asynchronous delivery of data between applications in an indirect way through an intermediary.

In multithreaded code, it is often common to use a single, master thread that drives the actions the other threads take. This master thread may send messages, often by placing them on a queue, that are then processed by the other threads. But if the master thread throws an exception, the remaining threads may continue to run, awaiting more input to the queue, causing the program to freeze. This article discusses detecting, fixing, and avoiding this bug pattern.

Web services and J2EE connectors promise to simplify the integration of heterogeneous enterprise information systems and provide a way for business partners to share their respective applications' functionality over the Internet. This article uses an insurance broker scenario, in which the programmatic functions from legacy transactions are incorporated into a Web application, to illustrate these capabilities.

Tags are reusable code libraries and allow easier separation of HTML and Java code. This tutorial first introduces JSP custom tags and then moves forward to build a simple JSP tag. Every step has been explained in detail. Online demo available.

This tutorial is second in a series of tutorials about JSP tags. In this tutorial we will learn what are scripting variables in JSP tags and how to make use of them. Online demo available.

The corporate firewall is a double-edged sword. It helps prevent unauthorized access to the corporate Web services, but can disable access for legitimate clients. Due to the number of safety measures taken by system administrators, HTTP has become the universal entry mechanism to the corporate network. Where technologies such as CORBA and DCOM have failed because of the firewall, technologies such as SOAP have been developed to provide safe and reliable access through firewall protection. This article explores an alternative to SOAP, the use of Java objects over HTTP. In addition, it uses J2EE servlet technology as server-side middleware to the business data.

The Java Database Connectivity (JDBC) API has emerged as a key part of the Java 2 Standard Edition (J2SE) and Java 2 Enterprise Edition (J2EE) platforms. It is the primary standards-based mechanism for the Java language to programmatically access relational databases, so when a new version of the specification is released by the Java Community Process, developers are bound to be interested. This article summarizes the key new features as outlined in Sun Microsystems' recently released Proposed Final Draft 3.0 of the JDBC specification.

Weblets are Java programs that run in a browser, using DirectDOM to directly manipulate displayed documents. Like most Web-based programs, weblets pose a threat to system security if they're mishandled. Fortunately, weblets come with built-in security in the form of the Java sandbox. This final installment of a three-part series on DirectDOM and weblet-based development shows you how to use the sandbox to your best advantage. With simple, working examples, this article demonstrates what a weblet can and can't do by default, and also shows you how to get around the constraints of the sandbox when the situation calls for it.

A step by step tutorial to create a JavaBean which detects user browser and .NET enabled status. You can use this bean to develop browser friendly pages. Online demo available.

An article on JavaBeans, answers questions like what JavaBeans are and how to create your own JavaBean. Online demo available.

This article discusses the anatomy of a JSP page. Discusses all the directives, scripting elements, actions and JSP tags which form part of the JSP page. This article provides good foundation for studying advanced JSP topics.