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. This is Jamaica's users' manual, including syntax for all JVM bytecode instructions and Jamaica macros. This is not meant to be a reference for the JVM, Java class files, JVM architecture and JVM runtime environment; they are introduced where necessary only to serve as the background for bytecode programming.