Recent technologies such as the Real-Time Specification for Java promise to bring Java's advantages to real-time systems. While these technologies have made Java more predictable, they lack a crucial element: support for determining the worst-case execution time (WCET). Without knowledge of WCET, the correct temporal behavior of a Java program cannot be guaranteed. Although considerable research has been applied to the \emph{theory} of WCET analysis, \emph{implementations} are much less common, particularly for Java. Recognizing this deficiency, we have created an open-source, extensible tool that supports WCET analysis of Java programs. Designed for flexibility, it is built around a plug-in model that allows features to be incorporated as needed. Users can plug in various processor models, loop bound detectors, and WCET analysis algorithms without having to understand or alter the tool's internals.