A program’s object model captures the essence of its design. For some programs, no object model was developed during design; for others, an object model exists but may be out-of-sync with the code. This paper describes a tool that automatically extracts an object model from the classfiles of a Java program. Unlike existing tools, it handles container classes, by inferring the types of elements stored in a container, and eliding the container itself. This feature is crucial for obtaining models that show the structure of the state, and bear some relation to conceptual models. Although the tool performs only a simple, heuristic analysis that is almost entirely local, the resulting object model is surprisingly accurate. The paper explains what object models are and why they are useful; describes the analysis, its assumptions and limitations; evaluates the tool for accuracy, and illustrates its use, on a suite of sample programs.