This page provides annotated links to the articles of my Under The Hood column, which I wrote for JavaWorld between June 1996 and December 1997. Most of the material in these articles made its way in some form into my book Inside the Java Virtual Machine.

The Articles

The Lean, Mean Virtual Machine (June 1996) -- provides an introduction the the Java Virtual Machine. It contains an applet, named Eternal Math, that simulates the Java Virtual Machine executing a sequence of bytecodes.

The Class File Lifestyle (July 1996) -- describes the format and function of the Java class file. It contains an applet, named Getting Loaded, that simulates a Java class file being loaded by a Java Virtual Machine.

Java's Garbage Collected Heap (August 1996) -- discusses garbage collection techniques in general and Java's heap in particular. It contains an applet, named Heap Of Fish, that demonstrates a mark and sweep garbage collected heap.

Bytecode Basics (September 1996) -- introduces the bytecode instruction set of the Java Virtual Machine. The article discusses primitive types, type conversion, and stack operation. It contains an applet, called Conversion Diversion, that simulates a Java Virtual Machine executing a sequence of bytecodes that perform type conversion.

Floating Point Arithmetic (October 1996) -- discusses the floating point mechanism of the Java Virtual Machine and introduces the bytecodes that perform floating point operations. It contains two applets. One applet, called Exposed Float, allows the reader to manipulate and observe a Java float. The other applet, Circle Of Squares, simulates the Java Virtual Machine executing a sequence of bytecodes that perform floating point multiplication.

Logic and Integer Arithmetic (November 1996) -- Describes the Java Virtual Machine's support for logical and integer arithmetic, and the relevant bytecode instructions. It contains two applets. One applet, called Exposed Int, allows the reader to manipulate and observe a Java int. The other applet, Logical Results, simulates the Java Virtual Machine executing a sequence of bytecodes that counts using only logical operations.

Objects and Arrays (December 1996) -- Describes how the Java Virtual Machine's deals with objects and arrays, and the relevant bytecode instructions. It contains an applet, called Three Dimensional Array, that simulates the Java Virtual Machine executing a sequence of bytecodes that initializes a three dimensional Java array.

Java Beyond the Browser: The Channel Metaphor. (December 1996) -- This article (an extra one--not actually part of the Under The Hood column) explains what Marimba Castanet is and how it addresses some of the constraints presented by Java applets. It includes an example Castanet channel, Artima WordSurfer, that is a simple English vocabulary flashcards drill. I change the words every Sunday, so if you subscribe to this channel you can get a fresh batch of fancy words to practice each week. To subscribe to the channel, just follow the instructions at the bottom of the article.

Exceptions (January 1997) -- Describes how the Java Virtual Machine deals with exceptions, and discusses the relevant bytecode instructions. It contains an applet, called PlayBall, that simulates the Java Virtual Machine executing a sequence of bytecodes that shows exceptions being thrown and caught.

Try-Finally (February 1997) -- Describes how the Java Virtual Machine deals with finally clauses, and discusses the relevant bytecode instructions. It contains an applet, called HopAround, that simulates the Java Virtual Machine executing a sequence of bytecodes that shows finally clauses in action.

Control Flow (March 1997) -- Describes how the Java Virtual Machine does control flow, and discusses the relevant bytecode instructions. It contains an applet, called SayingTomato, that simulates the Java Virtual Machine executing a sequence of bytecodes that shows a switch statement in action.

The Architecture of Aglets (April 1997) -- Describes the inner workings of aglets, IBM's autonomous Java-based software agent technology.

The Point of Aglets (May 1997) -- Analyzes the real-world utility of mobile agents such as aglets, IBM's autonomous Java-based software agent.

Method Invocation and Return (June 1997) -- Explains how the Java Virtual Machine invokes and returns from methods, including the relevant bytecodes.

Thread Synchronization (July 1997) -- Explains how the Java Virtual Machine performs thread synchronization, including the relevant bytecodes.

Java's Security Architecture (August 1997) -- Gives an overview of the security model built into the JVM and looks at the JVM's built-in safety features.

Security and Class Loaders (September 1997) -- Shows how the JVM's class loader architecture contributes to Java's overall security strategy.

Security and the Class Verifier (October 1997) -- Explains how the class verifier fits into the JVM's security architecture.

Java's Security Manager (November 1997) -- A look at the role played by the security manager in the JVM's overall security model.

Closing the Hood (December 1997) -- A farewell to the Under the Hood column and a look at what's next.