ADiJaC - Automatic Differentiation of Java Classfiles. This work presents the current design and implementation of ADiJaC, an automatic differentiation tool for Java classfiles. ADiJaC uses source transformation to generate derivative codes in both the forward and the reverse modes of automatic differentiation. We describe the overall architecture of the tool and present various details and examples for each of the two modes of differentiation. We emphasize the enhancements that have been made over previous versions of ADiJaC and illustrate their influence on the generality of the tool and on the performance of the generated derivative codes. The ADiJaC tool has been used to generate derivatives for a variety of problems, including real-world applications. We evaluate the performance of such codes and compare it to derivatives generated by Tapenade, a well-established automatic differentiation tool for Fortran and C/C++. Additionally, we present a more detailed performance analysis of a real-world application. Apart from being the only general-purpose automatic differentiation tool for Java bytecode, we argue that ADiJaC’s features and performance are comparable to those of similar mature tools for other programming languages such as C/C++ or Fortran.