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A list of recommended books covering topics covered by Inside the Java Virtual Machine is available at Books Related to the JVM.

Java Class File Obfuscation

• The Obfuscation Home Page has many links to obfuscation and decompilation tools and information.
• HashJava is a free Java class file obfuscator.
• Neil Aggarwal's Obfuscate and ObfuscatePro.
• PreEmptive Solutions, Inc.'s DashO Java class file optimizer and obfuscator.

Further Reading about Java Security

• Secure Computing with Java: Now and the Future (a whitepaper)
• Applet Security FAQ
• Low Level Security in Java, by Frank Yellin
• The Hostile Applets Home Page
• This page has information about authentication in JDK 1.1.
• Project Kimera describes an interesting procedure for testing bytecode verifiers for correctness.

Further Reading about Network Mobility

Here are a few articles I wrote for JavaWorld that describe other forms of network-mobile Java code:

• Java beyond the browser: The channel metaphor. This article 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.
• The Architecture of Aglets. This article explains the inner workings of aglets, IBM's Java-based autonomous software agent.
• The Point of Aglets. This article examines the significance of the mobile agent approach to developing network services. (This article will appear April 15th.)

An Audio Impression

Here's an applet that provides an audio impression of the way software feels now that it is free to zip across the network as class files. Just press the Flying Class Files button:

For some reason your browser won't let you view (or hear) this way cool Java applet.

Further Reading on the Java Virtual Machine

• For more information about the Java Virtual Machine, the first place to look is the specification. The book, Java Virtual Machine Specification, by Tim Lindholm and Frank Yellin is the official word. You can browse or download a free HTML version of this book at JavaSoft's web site.

• After the Java Virtual Machine Specification, you may want to refer to the book, Java Language Specification, by James Gosling, Bill Joy and Guy Steele. This book, which specifies the Java language, can give more insight into the inner workings of the Java Virtual Machine. You can browse or or download a free HTML version of this book at JavaSoft's web site.

Newsgroups

• The newsgroup comp.lang.java.machine is dedicated to issues related to the Java Virtual Machine.

Further Reading on Class Files

• Chapter 4, The Java Class File Format, from the Java Virtual Machine Specification by Tim Lindholm and Frank Yellin is also available online.
• The January, 1998 issue of Doctor Dobb's Journal contains an article on the Java class file written by Matt T. Yourst. This article, titled "Inside the Java Class File," is also published online .
• Why CAFEBABE? - an amusing discussion thread from comp.lang.java.

Tools for Viewing Class Files

• The JDK includes a tool, named javap, which disassembles class files.
• JavaDump makes an HTML listing of the contents of a class file.

Tools for Manipulating Class Files

• JavaStrip strips out debug information from class files.

Libraries for Parsing/Generating Class Files

• JAS, a freely Java bytecode assembler, includes source code for a library that generates Java class files.
• JCF is a freely available library for parsing Java class files
• Chuck McManis wrote and made available some Java classes that will dump out the contents of a Java class file.

Further Reading on the Lifetime of a Class

• The lifetime of a class is described in Section 2.16, Execution, from Chapter 5, Constant Pool Resolution, of the Java Virtual Machine Specification by Tim Lindholm and Frank Yellin. .

Further Reading on the Linking Model

• Chapter 5, Constant Pool Resolution, from the Java Virtual Machine Specification by Tim Lindholm and Frank Yellin is also available online. .
• Chuck McManis wrote an article for JavaWorld, named "The Basics of Java Class Loaders," that describes class loaders.

Further Reading about Garbage Collection

For an in-depth treatment of garbage collection, check out the book Garbage Collection: Algorithms for Automatic Dynamic Memory Management by Richard Jones and Rafael Lins.

Here are three papers that give good general overviews of garbage collection:

• Andrew W. Appel, "Garbage collection," in P. Lee (ed.), Advanced Language Implementations, MIT Press, 1991, chapter 4, pp. 89-100.

• Jacques Cohen, 'Garbage collection of linked data structures', Computing Surveys, 13(3), 1981, pp. 341-367.

• Paul R. Wilson, "Uniprocessor garbage collection techniques," Yves Bekkers and Jacques Cohen (eds.), Memory Management - International Workshop IWMM 92, St. Malo, France, September 1992, pp. 1-42.

Further Reading on Bytecodes

• Chapter 10, Opcode Mnemonics by Opcode, from the the Java Virtual Machine Specification lists the instruction set opcodes in numerical order.
• The bytecode reference in the O'Reilly JVM book is also available online.

Bytecode Assemblers

• JAS is a freely Java bytecode assembler that includes source code.
• Jasmin is a freely available Java bytecode assembler that is based on the JAS library.
• Java Bytecode Assembler whose input is similar to the output of javap. Use of this assembler is free for educational purposes only.

Further Reading on Threads and Monitors

• The form of monitor used by Java is just one of many different kinds of mechanisms that fall under the name "monitor". For an in-depth technical overview of monitors in general, check out this paper:
  
  

  BUHR, Peter A., FORTIER, Michel, and COFFIN, Michael H. 1995. Monitor Classification.
  ACM Computing Surveys, Vol. 27, No. 1, (March 1995), 63-107
  

• For a good overview of all the mechanisms used in coordinating or synchronizing threads, including monitors, see:
  
  

  ANDREWS, Gregory R., and SCHNEIDER, Fred B. 1983. Concepts and Notations
  for Concurrent Programming. Computing Surveys, Vol. 15, No. 1, (March 1983), 3-43
  
  

• For a complete description of the low-level rules Java Threads must follow, see Chapter 8, Threads and Locks, from The Java Virtual Machine Specification by Tim Lindholm and Frank Yellin. This chapter is basically a reprint of Chapter 17, Threads and Locks, from The Java Language Specification by James Gosling, Bill Joy, and Guy Steel. These chapters specify how threads must behave in every Java Virtual Machine implementation. The presentation is thick and mathematical. They are not what I'd call easy reading, but as they are the specification, they give the full story. You can read them online by following the links above.

A proposal for revising the specification of Java Threads is at: http://www.cs.umd.edu/~pugh/java/memoryModel/jsr.html