Jamaica, the JVM Macro Assembler, is an easy-to-learn and easy-to-use
assembly language for JVM bytecode programming. It uses Java syntax to
define a JVM class except for the method body that takes bytecode
instructions, including Jamaica's built-in macros. In Jamaica,
bytecode instructions use mnemonics and symbolic names for all
variables, parameters, data fields, constants and labels. Jamaica is a
simplified JVM assembly language. It does not support inner classes.
Variables are all method-wide and are strongly-typed.

Jamaica is a language facade for a Java class creation API,
JavaClassCreator. This API closely mimics the Jamaica language, allows
users to define a Java class with the same flow, and supports all the
Jamaica instruction set and macros.

Why Jamaica? Even with the rigid JVM architecture and verification,
creating JVM classes at bytecode level is still highly risky and
error-prone. With Jamaica, you can quickly experiment dynamically
creating classes; once done, mechanically convert the Jamaica source
code into JavaClassCreator API calls. Jamaica is currently the only
macro assembler for JVM, and serves this purpose very well. Please
visit these links:

http://www.judoscript.com/articles/jamaica.html
http://www.judoscript.com/articles/JavaClassCreator.html
http://www.judoscript.com/download.html