State Machines which one may view as code written in an abstract programming language, can be applied to other virtual machines and to other programming languages as well. The target readers are practitioners---programmers, implementors, standardizers, lecturers, students---who need for their work a complete, correct, and at the same time transparent definition, and an executable model of the language and of the virtual machine underlying its intended implementation. As a consequence, in our models for the language and the machine, we first of all try to directly and faithfully reflect, in a complete way, as far as possible without becoming inconsistent, and in an unambiguous yet for the human reader graspable way, the intuitions and design decisions which are expressed in the reference manuals [18, 23] and underlie the current implementations of the language and the machine. We clarify various ambiguities and inconsistencies we discovered in the manuals and in the implementations, concerning fundamental notions like legal Java program, legal bytecode, verifiable bytecode, etc. Our analysis of the JVM bytecode verifier, which we relate to the static analysis of the Java parser (rules of definite assignment and reachability analysis), goes beyond the work of Stata and Abadi [34], Qian [27, 28], Freund and Mitchell [16], and O'Callahan [26]. 1.1 The goals of the book 3 In this introduction, we give an overview of the general goals of the book, its contents, the structuring techniques we use for decomposing Java and the JVM, and the literature we used. For additional information on the book and updates made after its publication, see the Home Page of Jbook at http://www.inf.ethz.ch/~jbook. 1.1 The goals of the book Our main goal is not to write an introduction to progr...

We provide a modular high-level definition of the Java Virtual Machine (JVM) architecture. We decompose the machine into three components -- the loader, the bytecode verifier and the interpreter -- each for a hierarchy of four stepwise refined JVM program layers. These layers naturally correspond to the structuring of Java into sublanguages with imperative, procedural, object-oriented and exception handling features. We give our definitions in terms of Abstract State Machines, which have a simple but precise semantic foundation. As a consequence our JVM models can be verified and validated by machine supported mathematical analysis and standard simulation techniques. Furthermore, due to their abstract nature, the models can serve as a platform independent basis for the evaluation and comparison of different JVM implementations.