Immersing students in Java and the JVM, this text enables a deep understanding of the Java programming language and its implementation. It focuses on design, organization, and testing, helping students learn good software engineering skills and become better programmers. By working with and extending a real, functional compiler, students develop a hands-on appreciation of how compilers work, how to write compilers, and how the Java language behaves. Fully documented Java code for the compiler is accessible on a supplementary website.